Fix worker crash

- When deleting RN from puli, reset all commands
- When registering worker if no cmds were detected by the calling
  rendernode, reset existing commands in puli
Store comments in DB

previous behavior:
- changeListener are active on every field of tasks and TG
- no update is done in DB on table tasks and task_groups (would cause too many updates in cascade i guess)

new behaviour:
- filter listener to trigger changeEvent only when 'tags' field is updated
- change "addcomment" webservice to activate its listener (previous behavirou would only update an item of the dict which would not active the listener)
- catch update request to actually report it in DB (change of tags will be the only case of update for these tables)
Merge branch 'feature/comments_in_db' into develop