Allow the user to install the shipped plugin from the out of date plugin warning message.
Fix some bugs to do with 100% scrobble point
- we assume a track within 1 second of completion got to 100% 
- only allow the user to set scrobble point to 5% accuracy
- don't do the thing with m_trackToScrobble (looks like old code that once made sense, but not anymore)
- definitely don't scrobble the same track twice (extra check)
- move scrobble point setting (and other related) to the user settings class
Make the elapsed time of the stop watch more accurate, but sill only update the frame every half second.
Add a setting to turn on and off the 4 minute max scrobble point. Also:
- The scrobble point and 4 minute max now take affect on the current track
- Scrobble settings dialog updated. Still looks a bit terrible though.
Not-Mac build fix. No one else included the Mac iTunes plugin installer.