Bluetooth: Add Device Added and Device Removed management events

When devices are added or removed, then make sure that events are send
out to all other clients so that the list of devices can be easily
tracked. This is especially important when external clients are
adding or removing devices within the auto-connection list.

Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>