[2.0] Added more missing docblocks. Implemented a double-inclusion listener prevention in EventManager

[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).

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

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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.

Merged all identity maps into one in the unitofwork. identity map now properly works with hierarchies.