[tests] added support for PostgreSQL tests [closes #14]
[mapper] introduced enhanced orm SqlBuilder (BC break!)
[mapper] fixed unnecessary grouping (due to postgresql) [closes #19]
[reflection] fixed searching joining table primary keys when using schemas
[tests] added missing identity map check test
Revert "[entity] implemented getPersistedId() for entities with composite PK [closes #10]"

This reverts commit 16254dcd770341f155f8902c3695f9ee8dda437a.
[tests] proper integration tests lock
[tests] fixed weird nette/tester method run order