Moved back to UUIDs from BSON ObjectIds.

ObjectIds where causing to much trouble with Redis and jsonpickle. It would have required loads of of conversions from str and back. UUIDs where good enough before so they will do here. We can re-visit this in the future if they start to cause issues which I can't imagine they will.

The auth tests are now passing. There may still be some issues we will see with coverage once every package has been updated.

Also some of the posts stuff has been moved accross. Just enough at the moment to get the auth tests to pass.