[gnome-software/wip/rancell/reviews] (12 commits) ...Merge branch 'master' into wip/rancell/reviews

[Robert Ancell <rancell src gnome org>]

Summary of changes:

  32c2c00... Add a basic Ubuntu review plugin (*)
  fce495a... Updated Serbian translation (*)
  f90107a... Updated German translation (*)
  d636324... trivial: Add a translator comment (*)
  706ec84... New Dutch translation master 3.20 (*)
  4144bbc... Show a guide label for the different star values (*)
  fcc2aff... Update Dutch translation Master 3.20 (*)
  5b1ab4a... Updated Brazilian Portuguese translation (*)
  a8752c3... Always show available web-apps (*)
  98d03e9... Updated Slovak translation (*)
  b449376... Updated Spanish translation (*)
  a87559e... Merge branch 'master' into wip/rancell/reviews

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