acousticbrainz: latest adjustments
acousticbrainz: latest adjustments

* Readability and consistency
* Better logging: warn by default for attributes that were not found,
  but don't drown user with info when everything is going well.

shamangeorge/beets,SusannaMaria/beets,diego-plan9/beets,madmouser1/beets,madmouser1/beets,SusannaMaria/beets,madmouser1/beets,mosesfistos1/beetbox,diego-plan9/beets,beetbox/beets,MyTunesFreeMusic/privacy-policy,sampsyo/beets,xsteadfastx/beets,jackwilsdon/beets,ibmibmibm/beets,xsteadfastx/beets,ibmibmibm/beets,sampsyo/beets,Kraymer/beets,lengtche/beets,jackwilsdon/beets,lengtche/beets,SusannaMaria/beets,mosesfistos1/beetbox,MyTunesFreeMusic/privacy-policy,ibmibmibm/beets,mosesfistos1/beetbox,SusannaMaria/beets,jackwilsdon/beets,shamangeorge/beets,sampsyo/beets,shamangeorge/beets,xsteadfastx/beets,mosesfistos1/beetbox,beetbox/beets,artemutin/beets,madmouser1/beets,artemutin/beets,pkess/beets,MyTunesFreeMusic/privacy-policy,Kraymer/beets,xsteadfastx/beets,jackwilsdon/beets,lengtche/beets,diego-plan9/beets,artemutin/beets,sampsyo/beets,artemutin/beets,pkess/beets,ibmibmibm/beets,beetbox/beets,pkess/beets,MyTunesFreeMusic/privacy-policy,lengtche/beets,pkess/beets,diego-plan9/beets,Kraymer/beets,beetbox/beets,Kraymer/beets,shamangeorge/beets