Fixed a NPE that turned up when selecting an item in the contex menu of
the release list. As onContextItemSelected() is called on every fragment
instance of the fragment manager (not just the one that is displayed)
Fixed #1: Extended musicbrainzws2-java library so it allows for
customizing the user agent string.
Extended nusic app so the app name, version and URL are passed to
musicbrainzws2-java to added to each HTTP request as user agent.
Example: nusic/0.5 MusicBrainz-Java/2.01beta-nusicEdition (
https://github.com/schnatterer/nusic )