15 hours in a plane with in-seat power. Ok, time for some new features!

Added two new repository groups. 

"manual" can be used to avoid the assistant downloading any file contents
on its own. It'll still upload and otherwise sync data. To download files,
you can use `git annex get` while the assistant is running. You can also
drop files using the command line.

"source" is for repositories that are the source of new files, but don't
need to retain a copy once the file has been moved to another repository.
A camera would be a good example.

Ok, those were easy features to code; I suck at being productive on planes.
Release coming up with those, once I find enough bandwidth here in AU.
