[picard/f15] (5 commits) ...Update to 0.15.1 (latest upstream)

[alexlan]

Summary of changes:

  a2ee5c6... - Update to 0.15beta1 (#683055) - Convert plugin files to f (*)
  bddf068... Add missing Python files that were masked by .gitignore. (*)
  acb8345... Add new plugins. (*)
  f9356d8... Update coverart.py plugin. (*)
  01c08e3... Update to 0.15.1 (latest upstream) (*)

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