dbus: Add Device.Forget()
dbus: Add Device.Forget()

Add a new mthod to allow the users to remove a paired device. Removes
all meta-data associated to this device.

CESARBR/knot-service-source,CESARBR/knot-service-source,CESARBR/knot-service-source,CESARBR/knot-service-source,CESARBR/knot-service-source