[2.0] Fixed several referential integrity issues. Fixed critical issue with inserts being run twice on postgresql/oracle. Added support for additional tree walkers that modify the AST prior to SQL construction and started to play with it in a testcase.

[2.0] Implemented DQL bulk DELETE support for Class Table Inheritance. Other cleanups, refactorings and docblock additions.

[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.

reverting the reorganization done in 3455-3456 in order to make merging my experimental branch to trunk easier.

Preparation for new organization of code in to sub packages. Changed autoload() to work with new structure.

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