Moves star difficulty calculation entry-point to Beatmap, and sets star difficulty at the correct place for song select to display.
Note that this is a very naive approach and will result in file access exceptions. This will be fixed in a further commit.
They can now only be instantiated from BeatmapDatabase and are abstract (to avoid misuse).
Adds base classes for difficulty calculations, hooks them up with carousel container, and adds a port of the osu difficulty calculator.
Also makes the connection private.
Also fixes the broken IPC condition
Moves import code to BeatmapDatabase.
Also adds event that notifes the song select when a beatmap is added.