[2.0] Some code reordering, changes. Removed classMetadata from RangeVariableDeclaration, since it is against AST concept.

[2.0] Implemented DQL bulk UPDATE support for Class Table Inheritance. Corrections to MultiTableDeleteExecutor and SqlWalker. DQL bulk UPDATE support not yet fully complete.

[2.0] Fixed issues discovered during code coverage report generation. Made all ClassMetadata properties public (good reasons, read the class docblock). Performance improvements.

[2.0] Parser work. Added double-dispatch functionality to AST node classes for use in the SqlWalker to reduce big if/else instanceof checks and for better maintainability. Also its less error-prone in the SqlWalker because its harder to miss a conditional case. Added new extensible DQL function implementation.

DQL Parser work. Getting some first tests back running. Reorganizing all parser rules into the Parser itself.

Implemented new classes. Fixed a couple of issues around the road.