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.

This is particularly annoying for numeric functions like sqrt(...)
(example query: SELECT TOP 1 sqrt(2) as s2 FROM whatever_table).
This bug has been raised by M. Taylor.

functions must be casted into NUMERIC. Otherwise Postgres rejects the query.

(merge with branch 'unknownFctType')

[ADQL,TAP] Add geometry format in output and correct upload of STC-S regions. Geometrical type conversion from and into a DB type is now required in all JDBCTranslator. This allows formatting of geometrical column value coming from the database, but also the translation of STC-S expressions provided in uploaded table into geometrical column values.

[ADQL] Support the special escaping syntax for string literals in Postgres (strings to escape must be prefixed by a E before the starting ').

[TAP,ADQL] Improve and remake a part of the database connection. Missing javadoc has been added when missing in the modified tables.

ADQL: Fix big bug: no parenthesis in the SQL translation for ADQL constraints with parenthesis ( ex: A AND (B OR C)) )

ADQL: Correct version number for all modified ADQL related classes since the official v1.1 release. Now, version number after any modification in ADQL is v1.2.

ADQL: Completely change/improve Joins management, and particularly NATURAL JOIN and USING JOIN. Now, every joined columns are represented by a DBCommonColumn instance which has a given table coverage.
Before, there was a problem while using at least 3 or 4 NATURAL JOINs. Bug raised by Menelaos Perdikeas (ESAC).