[grilo-plugins] (7 commits) Non-fast-forward update to branch wip/jfelder/tracker-musicbrainz-external-reference

[Jean Felder <jfelder src gnome org>]

The branch 'wip/jfelder/tracker-musicbrainz-external-reference' was changed in a way that was not a 
fast-forward update.
NOTE: This may cause problems for people pulling from the branch. For more information,
please see:

 https://wiki.gnome.org/Git/Help/NonFastForward

Commits removed from the branch:

  b514b4b... tracker: Use tracker:ExternalReference to retrieve musicbra

Commits added to the branch:

  8863cb5... README: Convert README to Markdown (*)
  b925e4a... Update Brazilian Portuguese translation (*)
  a636a51... grl-tracker-utils: Add setters for new writable keys (*)
  7fa5126... grl-tracker-source-api: Add more keys to writable keys list (*)
  16e815b... tracker: Use the correct property to retrieve album title (*)
  af7d6b6... tracker: Remove musicbrainz keys from the list of writable 
  7c29d5e... tracker: Use tracker:ExternalReference to retrieve musicbra

(*) This commit already existed in another branch; no separate mail sent