plugin XEP-0334: fixed and improved message processing hints: - wrong elements were used in this plugging, it could not work properly - use constants for hints - add addHint method so other plugins can add a hint easily - hints can be added by frontends in mess_data['extra']['hints'] (serialized dict) or by other plugins using addHint - if history is skipped on message reception, mess_data['extra']['history']['skipped'] is set - introduced PLUGIN_INFO['usage'] for usage information for developers

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