Garbage collection

[poperigby]

This can be a process that does two things:

1. If a mod hasn't been referred to by a profile for a set amount of time, delete it.
2. If a Game/Profile/Mod exists on disk but not in the database, delete it. This should only be the case if the deletion function terminated prematurely or bugged out.

[Kruziikrel13]

In addition, replace rmdb with cli functionality for cleaning db. (Instead of just straight up rming target dirs)