MBS-4376, add /ws/js/cover-art-upload call + test.

Conflicts:
	postgresql-musicbrainz-collate
	postgresql-musicbrainz-unaccent
MBS-4376, Add filesize.js.
MBS-4376, port ajax uploader to knockout.js (work in progress).
MBS-4376, add event handlers to manipulate the list of images to upload.
MBS-4376, add submit_edit code.
MBS-4376, fix data sent by submit_edit so the edit is actually created.

Also:
- Don't start uploading until the image has been validated.
- Add some error text to each deferred.reject() call, which could help debugging.
MBS-4376, add mime-type.
MBS-4376, integrate fallback iframe into this multifile upload branch.
MBS-4376, Update progress bar during sign/upload/submit process.
MBS-4376, tests for CoverArt.js
MBS-4376, add cover art layout fixes.
MBS-4376, redirect back to /cover-art when all images have been submitted.
MBS-4376, use icon images from forms.less
MBS-4376, Add t/sql/cover_art_types.sql, which is used by script/setup_development_db.sh
MBS-4376, initialize the comment field with an empty string.
MBS-4376, patch File.prototype.slice on older browsers.
Merge branch 'mbs-4376-knockout' into beta

* mbs-4376-knockout:
  MBS-4376, patch File.prototype.slice on older browsers.
  MBS-4376, initialize the comment field with an empty string.
  MBS-4376, Add t/sql/cover_art_types.sql, which is used by script/setup_development_db.sh
  MBS-4376, use icon images from forms.less
  MBS-4376, redirect back to /cover-art when all images have been submitted.
  MBS-4376, add cover art layout fixes.
  MBS-4376, tests for CoverArt.js
  MBS-4376, Update progress bar during sign/upload/submit process.
  MBS-4376, integrate fallback iframe into this multifile upload branch.
  MBS-4376, add mime-type.
  MBS-4376, fix data sent by submit_edit so the edit is actually created.
  MBS-4376, add submit_edit code.
  MBS-4376, add event handlers to manipulate the list of images to upload.
  MBS-4376, port ajax uploader to knockout.js (work in progress).
  MBS-4376, Add filesize.js.
  MBS-4376, add /ws/js/cover-art-upload call + test.