It's the only plugin for which the implementation is done in the -plugin.c

- Remove the is_active() checks, the main daemon should be doing those
- Move the non-boilerplate code from -plugin.c to -manager.c
- Do everything at start-up either from an idle, or use the async functions
- Replace the "SimulateUserActivity()" call with something else (is it supposed to bring back the session when the screensaver was on?)