bridge (D-Bus): bad design fixes: - renamed outputed module to dbus_bridge (to avoid uppercase and conflict with dbus module) - class name is now Bridge for both frontend and core (make discovery/import more easy) - register renamed to register_method in core, and register_signal in frontend

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