use MPD's own database update time when checking for album cache

should fix cache update problems if the server's and the android client's
times are not synchronized, see #645
make backup of value before setting it
Jump to beginning of current song instead of previous if more than 5 sec have been played
Collapsed Albums: add setting
Collapsed Albums: add strings

Conflicts:
	MPDroid/src/main/res/values-de/strings.xml
Collapsed Albums: add PlaylistAlbum
Collapsed Albums: add size() and hasText() to AbstractPlaylistMusic
Collapsed Albums: add CollapsedPlaylistFragment
Collapsed Albums: use CollapsedPlaylistFragment
make playlist text autoscroll
make header in SongsFragment autoscroll
make Songs in SongsFragment autoscroll
autoscroll in albumfragment -- partially

Conflicts:
	MPDroid/src/main/java/com/namelessdev/mpdroid/views/AlbumDataBinder.java
show disc and track number in NowPlaying