Support listening on D-BUS to MPRIS implementation to trigger caffeine

[orontee]

Motivation

VLC, Rhythmbox, Video, clementine, etc. there are many applications implementing the D-BUS interface Media Player Remote Interfacing Specification. From my pov, they're exactly the applications that should trigger Caffeine.

It would be nice to have an option for Caffeine to listen to D-BUS to get enabled when an application advertise it's playing through its MPRIS interface.

Gain for users: They would not have to register application one by one any more!

[stuarthayhurst]

Is this a duplicate of #217?

I plan on tackling that at some point when I have more time, but if anyone wants to do it first you're more than welcome :)

[orontee]

Right, sorry for that.