#57 Groups support

[Skiron]

Model HD5 and E40x can create groups to sort titles. Groups seem to be different from playlists and album. They can be created and handled within SonicStage, so they should be handled in JSyphonic.

Pipo asked for this feature in GMP3 forum:
http://forum.generationmp3.com/index.php?s=&showtopic=58376&view=findpost&p=684284
and other users in Improvements/Groups thread:
https://sourceforge.net/apps/phpbb/symphonic/viewtopic.php?f=3&t=58