[2.0] Fixed and added some missing/wrong docblocks. Renamed Assigned to AssignedGenerator as scheduled to be renamed.

[2.0] DDC-239 - Added several new mapping validations for duplicate association/field and or column name definitions, and in combination with the discriminator column name.

[2.0][DDC-92] Fixed. Patch provided by Christian Heinrich. [DDC-274] Started some method renaming. [DDC-142] Fixed (join column names and discriminator column names dont support quoting) [DDC-258] Fixed.

[2.0][DDC-22] Fixed. Also cleaned up association handling. More to come: exception refactorings, proxy simplifications (single proxy class, not two).

[2.0] Fixes and enhancements to sequence generators. Test suite now runs & passes against postgres. Other minor, unrelated cleanups.