[2.0] More refactorings in Annotations parser and DQL parser. Now they only use constants instead of string processment

[2.0][DDC-49][DDC-50][DDC-33] Fixed DDC-49 and DDC-50. Also addressed DDC-33. Various other small changes and fixes. For problems with proxy objects please refer to the updated documentation.

[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] Finished reorganization of grammar rules in DQL parser source code. Renamed some private methods.

[2.0] Changes in DQL grammar for optimization purposes. Implemented new DQL grammar rules and did a couple of TODOs

[2.0] Updated semantical error to display token and text close to the found error. Some cosmetics applied.

[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.

[2.0] Parser work. Drafted logic for multi-table deletes through DQL (for Class/Concrete Table Inheritance)

Added getters to AST. Removed Production::__call. Added visitor support to AST. (guilherme: dont shoot me yet :-). visitor support doesnt hurt even if we do not use it for SQL generation). Lots of other things.

Refactorings and initial commit/draft of new event handling / configuration / bootstrapping. Still need to remove all the static EntityManagerFactory::getManager lookup calls from the Production classes. The production classes need to have access to the EntityManager of the Query that constructed the Parser. It should be injected into the Parser during construction.

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.

Finished first parts of SELECT support. Two test cases added and passing. Introduced the concept of DCTRN in queryComponent. Added concept of queryField, which validates for already defined fields in SELECT.