Improvement: initial DBUS server handling (draft) that allows querying
or changing properties on the fly (aka executing methods via dbus), for
now we implemented "getProperty", "setProperty" and "reset" methods calls.
They are rather basic and not very bounds checked or supposed to work
smoothly but is indeed a start (be able to communicate with the

Example of sending a message:
- start compton with the dbsu option
  $ compton --enable-dbus
- in another terminal issue one of those commands
  $ dbus-send --print-reply --dest=com.compton.server /com/compton/Object com.compton.Options.getProperty string:"vsync"
  $ dbus-send --print-reply --dest=com.compton.server /com/compton/Object com.compton.Options.setProperty string:"vsync" string:"opengl"
  $ dbus-send --print-reply --dest=com.compton.server /com/compton/Object com.compton.Options.reset

Obviously this needs to be refactored and improved MUCH, but at least is a starting point.