Add a CAN_LOOP capability flag
Add a CAN_LOOP capability flag

Rationale:

Media players do not always have the ability to loop through the tracklist,
for instance when playing an endless media stream like a web-radio. However,
the current MPRIS provides no way for them to indicate that.

Changes:

 * Add the CAN_LOOP flag as part of the capabilities bitfield with a
   value of 1 >> 8

mirsal/mpris