This commit reverts commit 89418d13.

The reverted commit will be applied in another branch (probably 'adql-2.1') as
it is part of the next release of ADQL-Lib.

- Now, `ADQLParserFactory.createParser(...)` should be used to create a parser
- Only the new function `LOWER` is supported for the moment
- Not yet possible to manage the optional features _(next dev to come)_
=> 1st step for ADQL-Lib v2.0

- TAP adapted so that using the last stable version of the ADQL language
  (i.e. 2.0 for the moment)
  - but not yet possible to set the ADQL version to use in the configuration
    file

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.

[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,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,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).

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