Cleanup unused files

- unused pom.xml and *.iml files
Allow for easy re-testing of the same API with abstract test classes

- Created abstract test classes for SequenceCollection and
SequenceCollectionFactory
- Abstract test classes, have good coverage of the tests and through
extending them, and making the appropriate SequenceCollectionFactory
available via the getFactory() method you can quickly establish quality
of code for a collection.