Port MPRIS (D-Bus service) plugin to C

Submitted by Bastien Nocera @hadess

Link to original bug (#680319)

Description

So it can be enabled by default.

See also: https://github.com/media-explorer/media-explorer/commit/8c9736acf32d829f611c38969095f6784d5af572 http://cgit.freedesktop.org/xdg/mpris-spec/tree/spec/Player_Node.xml