[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.

DQL Parser work. Getting some first tests back running. Reorganizing all parser rules into the Parser itself.

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.

Added new exception classes, renamed Doctrine_Repository to Doctrine_Table_Repository, refactored many classes

removing the closing PHP tags form all php files, it\'s not needed and can break sessions which are whitespace sensitive

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