[2.0] More general work on the SchemaManager and Platform classes. Making API more complete and adding sqlite and mysql test coverage.

First tests for basic collection implementation. First experimental use of closures (Currently commented out, because the svn server makes a syntax check against 5.2.x).

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

merged fix for #912 from 0.10 to trunk (turned out it was not broken in trunk but i merged the patch & testcase anyway. Other refactorings.

started refactoring to final mapper structure for 1.0. different mapping strategies are factored out as separate strategy classes instead of inheritance.

Merged r3518:r3700 from branch to trunk. Branch to be deleted, soon. Development continues in trunk.

- unified getDefaultFieldDeclaration(), force DEFAULT NULL when no default is set and the field allows nulls

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.

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