`fix_on_fail` in the configuration file. By default, this feature is disabled.

_With 15cd5944, this commit finishes the resolution of the GitHub issue #104 ._

Before this fix, cancelling a TAP job (async or not) which was formatting the
result in ASCII may failed, especially for large results. This was due to a
non interruptible alignment process. This process is now checking whether a
cancellation has been requested before formatting a new result line/row ; if so,
the process is immediately stopped and the job can be cleaning declared as
aborted.

The property `upload_default_db_limit` has been deprecated. Indeed, in the
current state of the TAP protocol, this makes no sense: the user can not change
the limit size (in bytes or rows) for uploaded tables.

The property `upload_max_file_size` has been deprecated. It is actually
duplicated: `upload_max_db_limit`, if expressed in bytes already lets put a
limit on the maximum size of an uploaded table/file.

The property `upload_max_request_size` has been added. It lets set a maximum
size for a whole HTTP Multipart Request. By default it is set to 250MB.

The default value of `upload_max_db_size` is now 1 million rows.

The UPLOAD feature is still disabled by default (i.e. `upload_enabled=false`).

Then, UWS or TAP implementors are free to use whatever logging system they want
(e.g. log4j, logback, ...).

This commit resolves partially the issue #28

Ideally, there should be an implementation of UWSLog and TAPLog working with
Log4j and another for SLF4J (and eventually for other logging mechanism).
Additionally, an implementation storing log messages in database would be
interesting. All these ideas may be implemented in UWSLib and TAPLib in a
future version.

On the contrary to other DBMS, MySQL supports schemas, but as databases.
Which means that JDBCConnection gets from the JDBC driver that MySQL does
not support schemas and so it tries to access TAP_SCHEMA tables with a
'TAP_SCHEMA_' prefix instead of 'TAP_SCHEMA.' one. Since MySQL does
behave like it supports schemas, JDBCConnection.supportsSchema must be
set to 'true' if the DBMS is MySQL.

Besides, since no schemas are returned by the JDBC driver
(cf DatabaseMetadata.listSchema(...)), the function
JDBCConnection.isSchemaExisting(String, DatabaseMetaData) must always assume
that the specified schema exists if the DBMS is MySQL. This is particularly
important when the existence of 'TAP_UPLOAD' must be checked, because if the
function returns 'false' the library will attempt to create the database/schema
'TAP_UPLOAD' and will obviously fail due to a lack of permissions. Of course,
it means that the TAP implementor must create manually the schema/database
'TAP_UPLOAD' him-/her-self.

The second particularity of MySQL is the quote character for identifiers.
It is a back-quote (`) instead of a double quote ("). To reflect this
difference, JDBCTranslator.appendIdentifier(...) has been overwritten in a new
JDBCTranslator extension: MySQLTranslator.

The translation of all SQL types and mathematical functions have been adapted to
MySQL according to the online documentation. Few tests have been done locally
with a tiny database. This seems to work but further testing should be
performed in order to ensure the stability of this implementation.

Two embedded DBMS are used: H2 and a little SQLite. JDBC drivers are provided
in the `lib` directory. The databases are created and deleted automatically
by the JUnit tests (see `test/tap/db_testtools/DBTools for more details`).

The ANT and Gradle build scripts have been updated to reflect all these test
modifications.

with a constructor having a Properties object loaded with the content
of the current configuration file.

Can be enabled just by providing a file URI in the TAP configuration file using
the property "examples". It is also possible to add manually a TAP resource
whose the returned name must be "examples" like the new TAP resource is doing:
tap.resource.Examples. This latter take a file URI as the TAP configuration
file does. The referenced file must respect the DALI 1.0 or TAP Notes 1.0
syntax. No check of the file is performed by the library ; it is up to the
author of the referenced file (a XHTML/RDFa file) to write a correct "examples"
endpoint content. Check out the examples provided on the GitHub repository in
the directory examples/tap/examples_endpoint.

[TAP] Fix NullPointerException in TAPConfiguration (this error happens only when a NoSuchMethodException occurs.

[TAP] Add Javadoc for all TAP configuration file related classes + Improve the function ConfigurableServiceConnection.getFile(...) + Set the default value of limits/durations/periods to the maximum value if the new maximum value is less than the current default value.

[TAP] Incorrect setting of the backup frequency. The documentation was also incomplete about this property, but also wrong concerning the property backup_mode which is actually backup_by_user.

[TAP] Add the possibility to set the FetchSize on a DB Statement for the execution of ADQL queries. It is also possible to set a fetchSize different for synchronous and asynchronous queries.

[TAP] Add a configuration file property: 'coordinate_systems'. It lets list all allowed coordinate systems. By default, the list is empty, meaning that any is allowed.

[TAP] Rename the property 'output_add_formats' into 'output_formats' & Correct the name of the service description in tap_full.properties.

[TAP] Change the default value for output and upload limits ; only negative value must mean 'no restriction' ; 0 must be a normal allowed value.

[TAP] Add a property in the configuration file to set a custom TAPFactory (in replacement of ConfigurableTAPFactory.

[TAP] Add a 3rd possibility to set metadata in the TAP configuration file: give an extension of TAPMetadata having either an empty constructor or a constructor with a UWSFileManager, a TAPFactory and a TAPLog. & Rename function TAPConfiguration.isClassPath(String) into TAPConfiguration.isClassName(String).

[TAP] Add property to add/replace TAP resources & Add the tool function TAPConfiguration.newInstance(...).

[TAP] Add log management in the TAP configuration file. 2 additional properties have been added: min_log_level and log_rotation.

[TAP] Add missing formats (particularly all the different VOTable serializations) in the TAP configuration file

[TAP] Fix Class loading MAJOR BUG: do not use a specific ClassLoader, but Class.forName(String). The ClassLoader is different in a WebApplication than in a standalone ; TAP.fetchClass(...) worked before in a standalone but not in a WebApplication.

[TAP] Add a new database access method in the configuration file: get a Datasource from JNDI. & Better support of connection pooling (TAPFactory.countFreeConnections() has been removed ; when the creation of a database connection fails with an SQLException, it is considered that no connection are momentarily available...async jobs will be queued and all sync requests will be rejected).

[TAP] Add support for user identification in the configuration file. Besides, each time a property expected as an integer is not an integer, an exception is thrown.

[TAP] Add a parameter to limit the number of running asynchronous jobs in the configuration file: max_async_jobs.

[TAP] Add metadata support in the configuration file. Two methods to get metadata: 1/ Parse an XML file implementing the schema TableSet, and then re-build TAP_SCHEMA in the database, 2/ Get metadata from the database schema TAP_SCHEMA.

[TAP] Remove the availability fields from the configuration file. The Service will always start as available ; there is indeed no reason to start and leave it as unavailable.

+ Add the management of the Output Limit in TAPConfiguration
+ All the corresponding JUnit Tests
+ Replacing .properties test files for JUnit by a construction of Properties object
+ Update of the HTML documentation page and of the Full example file

TAP+TEST: First steps with the TAP configuration file management (Factory, ServiceConnection, but not yet Metadata) + their JUnit tests + documentation (the html file + configuration file examples)