DataManager, LocalDataSource & Associated stuff

I think that the DataManager & LocalDataSource stuff is working well enough that we can integrate it at least. Still needs more work, but the basic methods seem to be working correctly, if not in the most efficient way possible.
Because I removed Inherit, due to the fact that it's not actually possible for most of the functions that rely on AuthoredItem to actually tell what the parent's mode is due to the way our APIs are set up.