[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)'.

ADQLObject has now a new function: getPosition(). To allow it, the parser and all ADQL query tree item have been modified to define this function properly. The parser is setting this position for all parsed items. The test class/main function "TestGetPositionInAllADQLObject" aims to check that after a parsing all items really have a defined position.

ADQL: Provide the position of any column reference (column in ORDER and GROUP BY) when returning a ParseException

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

1/ let the function ROUND having 2 parameters
2/ wrap Operations (WrappedOperand) with brackets when there are brackets in the ADQL query

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: Fix an ADQL bug (raised by Dave Morris) in the management of subqueries: before, it was impossible to use (in a clause different from the FROM) columns of a father query inside a subquery.

Becareful with the function addMatch(ADQLObject, ADQLIterator): the iterator may be null if the match to add is the root search object itself!
No modification needed in SimpleReplaceHandler: Null test already done :-) !

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).

ADQL: Fix ArrayIndexOutOfBoundsException while initializing a DefaultUDF (User Defined Function) object with several parameters.