media-api: Change RegisterPlayer to use MPRIS spec
media-api: Change RegisterPlayer to use MPRIS spec

RegisterPlayer now expect registered paths to implement
org.mpris.MediaPlayer2.player interface accourding to MPRIS spec:

http://specifications.freedesktop.org/mpris-spec/latest/

ComputeCycles/bluez,pstglia/external-bluetooth-bluez,silent-snowman/bluez,pstglia/external-bluetooth-bluez,pstglia/external-bluetooth-bluez,silent-snowman/bluez,silent-snowman/bluez,mapfau/bluez,pkarasev3/bluez,ComputeCycles/bluez,ComputeCycles/bluez,silent-snowman/bluez,mapfau/bluez,mapfau/bluez,pkarasev3/bluez,pstglia/external-bluetooth-bluez,ComputeCycles/bluez,pkarasev3/bluez,mapfau/bluez,pkarasev3/bluez