Fix various documentation/typos; remove a few superfluous things.
Fixing test that was accidentally broken.
Merge remote-tracking branch 'origin/topic/jsiwek/plugins-cleanup' into topic/robin/plugins

Adding one todo back in as that's something we indeed still need to do.

* origin/topic/jsiwek/plugins-cleanup:
  Fix various documentation/typos; remove a few superfluous things.