Cleaned up RepositoryManager interface. Moved lots to test repository manager as not needed unless in test environment.
Added a Repositories object that can be used to cache RepositoryManagers.
Merge pull request #81 from elvisisking/vdb-deriver-4

Cleaned up RepositoryManager interface. Moved lots to test repository manager as not needed unless in test environment. Added a Repositories object that can be used to cache RepositoryManagers.