config/ext: Automatically disable extensions with bad config
config/ext: Automatically disable extensions with bad config

Ensures config errors on extensions don't block mopidy startup. Also improves
error messages for config problems.

liamw9534/mopidy,pacificIT/mopidy,bencevans/mopidy,mokieyue/mopidy,quartz55/mopidy,swak/mopidy,mokieyue/mopidy,dbrgn/mopidy,swak/mopidy,ZenithDK/mopidy,jmarsik/mopidy,SuperStarPL/mopidy,quartz55/mopidy,hkariti/mopidy,rawdlite/mopidy,tkem/mopidy,pacificIT/mopidy,adamcik/mopidy,rawdlite/mopidy,SuperStarPL/mopidy,diandiankan/mopidy,woutervanwijk/mopidy,mopidy/mopidy,SuperStarPL/mopidy,tkem/mopidy,jmarsik/mopidy,tkem/mopidy,kingosticks/mopidy,ali/mopidy,swak/mopidy,hkariti/mopidy,diandiankan/mopidy,bencevans/mopidy,swak/mopidy,jcass77/mopidy,vrs01/mopidy,mopidy/mopidy,jcass77/mopidy,rawdlite/mopidy,priestd09/mopidy,pacificIT/mopidy,ZenithDK/mopidy,bacontext/mopidy,SuperStarPL/mopidy,ali/mopidy,jmarsik/mopidy,bacontext/mopidy,diandiankan/mopidy,quartz55/mopidy,mokieyue/mopidy,jodal/mopidy,bencevans/mopidy,bacontext/mopidy,glogiotatidis/mopidy,ali/mopidy,kingosticks/mopidy,diandiankan/mopidy,jodal/mopidy,dbrgn/mopidy,adamcik/mopidy,jodal/mopidy,glogiotatidis/mopidy,priestd09/mopidy,pacificIT/mopidy,rawdlite/mopidy,bacontext/mopidy,jcass77/mopidy,vrs01/mopidy,glogiotatidis/mopidy,ali/mopidy,ZenithDK/mopidy,liamw9534/mopidy,tkem/mopidy,mokieyue/mopidy,bencevans/mopidy,woutervanwijk/mopidy,priestd09/mopidy,quartz55/mopidy,adamcik/mopidy,mopidy/mopidy,dbrgn/mopidy,kingosticks/mopidy,dbrgn/mopidy,hkariti/mopidy,jmarsik/mopidy,vrs01/mopidy,hkariti/mopidy,glogiotatidis/mopidy,vrs01/mopidy,ZenithDK/mopidy