[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)

[2.0] More progress on the DQL parser. Added glimpse() method for the scanner/lexer that is equivalent to peek() immediately followed by resetPeek().

More DQL parser work. First basic WHERE conditions. Changed scanner according to new positional parameter syntax (?<number>)

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

Implemented new classes. Fixed a couple of issues around the road.

Fixes Strict error on EntityPersisterMock.