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
Merge pull request #156 from aplanas/master

More idempotent refactor and fix for action #2460
fix new packages
Display requests as markdown lists in the comments
Merge pull request #158 from ancorgs/comment_requests_as_list

Display requests as markdown lists in the comments
retried_POST should stop for 504
give ancor something to review
Merge pull request #159 from openSUSE/coolos_evil_plan

give ancor something to review
parse all changes
Small refactor. Remove tabs.
Fix a bug in the yield value.
Move out memoized functions.