Remove some dead code.

Deleted a number of functions that were made unnecessary by an
earlier refactoring.
Apply some minor refactoring to Database.hs

Assorted minor code cleanup. No change in functionality.
Require MonadDB instances to also be Applicative instances

Some code that I ended up throwing away needed MonadDB instances
to also be Applicative instances. Even though that code was
abandoned, MonadDB really should be Applicative, so I'm checking
the change in anyway.
Export some MediaController functions from Core
Implement proper main function

Gramophone.main now has command line option to load or create
a database before starting the Web GUI.