quick_frontend, primitivus: various fixes (MUC and cached signals): - actually call the cached signals, everything was there but the call was not done - display '[]' instead of '[None]' when group message coming from the room (no resource) - catch the exception when trying to delete an occupant who's not in the room - do not cache a "main resource" for MUC entities

Use this module to temporary store files that need to be integrated to other
projects such as Wokkel.

For example, the changeset that introduced this folder adds RSM (XEP-0059)
support to Wokkel. The files in sat.tmp.wokkel are imported over the initial
wokkel files from sat.plugins.__init__.py