Need l(ed)sd - daemon to interface with LEDs on devices

With #87 (closed) being the session part we want a system dbus service that exposes the lets for feedbackd (or whatever) to connect to. The hard part is not accessing the leds but coming up with some clever tagging so the leds can be accessed by a feedback-theme (instead or putting out raw led names). I have some prelimeanary code to make that happen.