don't make 2 db queries for channel.first
remove Channel definition check
Merge branch 'v3-channels' of https://github.com/play/play into v3-channels
use current_mpd errwhere
show mpd state error messages WITHOUT interrupting auth, via crime
Merge pull request #332 from play/v3-channels-auth-problems

show mpd state error messages WITHOUT interrupting auth, via crime
merge v3-channels