This is easily possible for concatenations, string constants and User Defined
Functions having a FunctionDef. A new special datatype was needed for
numeric functions and operations: UNKNOWN_NUMERIC. This special type
can not be set with FunctionDef.parse(...) and it behaves exactly like the type
UNKNOWN, except that DBType.isNumeric() returns true (as .isUnknown()).
Thus, while writing the metadata of a result in TAP, nothing changes:
an UNKNOWN_NUMERIC type will be processed similarly as an UNKNOWN type:
to use the type returned from the database ResultSet or to set VARCHAR.
(no modification of TAP was needed for that)

Functions whose some parameters are another function were not correctly
identified: since the inner functions were not yet identified, their type
was UNKNOWN and so it makes the identification of the parent function
much easier since an UNKNOWN parameter is not checked. But, it was a
problem if the parameter occurs to be finally of the wrong type.

(indeed, a Concatenation object has no name).

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

Now, all occurences of ' are replaced by '' in the SQL translation.

types. The notion of "unknown type" is different in function of the target
object:
  - a DBType and a FunctionDef have an unknown type if their function
    isUnknown() returns true. In such case, the other functions such as
	isNumeric/String/Geometry() will return false.
  - an ADQLOperand (e.g. ADQLColumn) does NOT have a isUnknown() function.
    But if the type of the operand is unknown, its functions isNumeric(),
	isString() and isGeometry() must ALL return true. Otherwise, just one of
	these functions can return true.

[ADQL] Fix a Big Bug reported by M.Taylor and M.Demleitner: in ORDER BY, GROUP BY and USING only regular and delimited identifiers are accepted, not qualified column names.
For instance: "SELECT table.column_name FROM table ORDER BY table.column_name" is wrong. We should instead write:
"SELECT table.column_name FROM table ORDER BY column_name".
"SELECT table.column_name AS mycol FROM table ORDER BY mycol" is also correct.
Of course, for ORDER BY and GROUP BY, it is still possible to reference a column using its index in the SELECT clause.
For instance: "SELECT table.column_name FROM table ORDER BY 1".

when in a table definition (extension of DBTable) no schema is
specified, it was possible to prefix the table name by a fake
schema name ; it was checked at all:
e.g. "SELECT * FROM no_schema.foo".
This is no longer possible: if no schema is specified, no schema
must be used in an ADQL query. But if one is specified, the schema
prefix is optional.

1/ Bad parsing of UDF's parameter type or return type. Database types whose the
name has a space (e.g. 'double precision') were not accepted. These type names
should be accepted according to TAPRegExt.
2/ An error message thrown by the DBChecker has been modified for the cases
the type of a parameter is unknown. Before the returned type was NUMERIC. Now,
it will be 'param' followed by the parameter index (e.g. 'param1').

(merge with branch 'unknownFctType')

[ADQL] Fix the ADQL DEBUG mode ; now ADQLParser.setParser(boolean) is doing what it is supposed to do.

[ADQL] Fix merge side-effects (e.g. '' were not translated any more as a single ' ; NullPointerExceptions when building positions) + transform the test main class for positions into a JUnit test case + Fix some position mistakes.
(note: a tabulation character seems to be interpreted by JavaCC as 8 characters)

[ADQL] Fix DEBUG mode in the ADQL parser. It is still by default disabled, but now, it is possible again to enable it using the function 'setDebug(boolean)'.

Replace uses of String.isEmpty and Arrays.copyOf methods
(both introduced in java 6) with equivalent code that makes
use of only methods available in the java 5 runtime.
This allows the ADQL library, if cross-compiled for java 5,
to run without errors on a java 5 runtime.

[ADQL] Rename UnresolvedJoin and UnresolvedFunction so that normalizing all UnresolvedXxx exceptions.

[TAP] Add an XML TableSet parser. The main modification done in JDBCConnection is about the schema prefix of table when the DBMS does not support schemas: now, only standard tables are expected with the prefix 'TAP_SCHEMA_' and the upload tables also with 'TAP_UPLOAD_'.

[ADQL] Keep the same order of columns as they are added inside the DBTable => use a LinkedHashMap rather than a HashMap

[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 ').

[ADQL,TAP] Add STC-S and UDFs support in the ADQL parser. Now, it is possible to provide a list of allowed UDFs, regions and coordinate systems. The ServiceConnection of TAP is now able to provide these lists and to propagate them to the ADQLExecutor. UDFs and allowed regions are now listed automatically in the /capabilities resource of TAP. The type 'geometry' is now fully supported in ADQL. That's why the new function 'isGeometry()' has been added to all ADQLOperand extensions. Now the DBChecker is also able to check roughly types of columns and UDFs (unknown when parsing syntactically a query). The syntax of STC-S regions (expressed in the REGION function) are now checked by DBChecker. However, for the moment, geometries are not serialized in STC-S in the output....but it should be possible in some way in the next commit(s).

[ADQL] Remove useless Javadoc (no custom javadoc for files automatically generated from the JavaCC grammar)

[ADQL] Fix table copy bug: the catalog and schema names where not copied or not interpreted when they were prefixing the new table name. WARNING: The copy function of a DBTable has a slightly different behaviour than before.

[ADQL] Fix SQL translation of NOT BETWEEN (before it was translated by just BETWEEN ; NOT was forgotten)

[ADQL] Fix SQL translation of operations' alias: now, the alias is always surrounded by double quotes (so a sum between two numbers won't have the default alias +, but it will have +)

[TAP] Remake TAPFactory into an abstract class + let limit the number of jobs (async and sync) by allowing the TAPFactory to communicate with a connection pool

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

[TAP] Remove all generic types + Delete specific (for ResultSet) output formatters + Modify the main output formatter