Review #89

This implements the changes Sam wanted in order to reduce the confusion over media enabled-ness, in particular:
- "Media Enabled" pref now only controls "AudioStreamingMedia"
- No more "tentative" state
- New "Music Enabled" pref
- First run dialog controls Media and Music (Sam, this is a change from your request...I think it works better)
- Put a reflection of the "Media Enabled" checkbox in the Nearby Media Floater
- Get rid of the "AudioStreamingVideo" setting altogether (whatever used it, it should now obey "AudioStreamingMedia").