plugin events: separation of event node and invitees node - event node is handling the main metadata of the event, and invitees node handle the invitations/invitees answers - invitees and blog node are automatically created and associated to the event, except if they are specified (in which cas the existing one are used and attached to the event node) - extra metadata are added to <meta> elements

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