[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.

[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).

Fixed paths that were referring wrong namespace resolution.
Implemented more Parser and AST classes: JoinVariableDeclaration and Join.
Fixed wrong semantical checks of IndexBy grammar rule. They should be in IdentificationVariableDeclaration and JoinVariableDeclaration.

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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.

Makes it easier to see the dependencies between these two concerns, cache the results of the query parsing process later on, implement & use alternative hydrators to experiment with different algorithms etc. etc.
Other small refactorings.