Merge branch 'dbtests' into merge

* Add classes Validator and ValidatorTestCase.
* Add new class ORMObject and ORMObjectTestCase.
* Refactor the fixture setup in PackageTestCase.
* Improve queries in dbconn.py using with_parent().
* Drop class SrcAssociation.
* Create, test, and improve get_suite_version().
* Create, test, and improve get_newest_source().
* Test and improve package_to_suite().
* Test and Improve source_exists().
* Remove some useless session.flush() calls.
* Refactor add_dsc_to_db().
* Test function add_dsc_to_db()
* Test and refactor get_suites_source_in().
* Refactor get_source_in_suite().
* Test the DBSource and Suite relation.

Signed-off-by: Torsten Werner <twerner@debian.org>