Add federated repository fetching methods to repository manager
Add PoddArtifactManager.getSchemaImports to enable selection of the
permanent repository location based on which schemas are being imported
by the given artifact
Implement new methods in PoddRepositoryManagerImpl
implement and use new methods in PoddArtifactManagerImpl
Use new methods in upload artifact resource impl

Add fixme note about pushing the relevant function into
PoddArtifactManager
Use new method in AddObjectResourceImpl
Migrate PoddSchemaManagerImpl to use new repository manager methods
Migrate methods in PoddFileRepositoryManagerImpl
migrate PoddRepositoryManagerTest
Migrate PoddFileRepositoryManagerImplTest
Migrate AbstractPoddFileRepositoryManagerTest to new repository methods
Migrate PoddArtifactManager test to new methods, roughly...
remove runtime exception to see how many tests still work