[2.0] Moved code between Query and AbstractQuery. Added first NativeQuery implementation. Hydration work and code movements for discriminator column usage. Started implementing Single Table Inheritance.

[2.0] Refactored SQL query building process and hydration. Hydration should now support result sets with any number of root components. Introducing ResultSetMapping that is used by hydration instead of queryComponents. This allows mapping of arbitrary SQL queries (NativeQuery).

First tests for basic collection implementation. First experimental use of closures (Currently commented out, because the svn server makes a syntax check against 5.2.x).

Fixed paths that were referring wrong namespace resolution.
Implemented more Parser and AST classes: JoinVariableDeclaration and Join.
Fixed wrong semantical checks of IndexBy grammar rule. They should be in IdentificationVariableDeclaration and JoinVariableDeclaration.

Changed Doctrine_Query to accept a Doctrine_EntityManager instead of a Doctrine_Connection. Updated Doctrine_EntityManager. Updated test cases and included one new passing test case for SELECT generation. Fixed whitespace bug in DELETE and UPDATE statements.

made sure every caller of getIdentifier can handle an array. getIdentifier now always returns an array.

Merged r3518:r3700 from branch to trunk. Branch to be deleted, soon. Development continues in trunk.