ignore firebird in dtc tests
changed id mapping from native to assigned and modified NorthwindDbCreator accordingly
retrieve id values when saving the entities and use them later in the test
ignore firebird since it has issues with comments containing apostrophes
added LEFT function to Firebird dialect
check the dialect through the right GetDialect overload
override AppliesTo(Dialect) instead of checking the dialect twice
trim 'Type' in property setter
remove unnecessary try/catch blocks
delete children first then the rest
clear the pool after the test