Write only one comment per action

 * For every 'select' or 'unselect' a single comment is written in
   every affected project
 * Previous automatic comments are deleted (as a first approach)
 * For more info, see https://progress.opensuse.org/issues/2564
Save some eye bleeding to pythonists
Small optimizations in the new code
Use markdown comments to hide the mark on generated OBS comments
Merge pull request #157 from ancorgs/status_comments

Write only one comment per action