Handle Bluetooth short UUIDs (uuid16)

[ukBaz]

Bluezero should be able to handle UUIDs in a couple of different formats.
It should be supported for people to add UUIDs without the dashes and to enter 16-bit UUIDs if they a official Bluetooth support values. A Base UUID is used for calculating 128-bit UUIDs from short UUIDs

BASE_UUID = 00000000-0000-1000-8000-00805F9B34FB

An example of what could be added is:

def _add_uuid_dashes(uuid):
    return '{0}-{1}-{2}-{3}-{4}'.format(uuid[0:8], uuid[8:12],
                                        uuid[12:16], uuid[16:20], uuid[20:])

def _valid_uuid(uuid):
    if len(uuid) == 32:
        return _add_uuid_dashes(uuid)
    elif len(uuid) == 4:
        return '0000{0}-0000-1000-8000-00805F9B34FB'.format(uuid)
    else:
        return uuid