binding: bluetooth-pbap: add import verb to improve transfer of contacts

binding: bluetooth-pbap: add import verb to improve transfer of contacts

Previously contacts are requested on every connection of a device by
OBEX transfers, and due to issues with transfer rates it should be only
done when requested.

import verb requests new phonebook transfer, and returns data as the
contacts verb currently does.

Also this patchset switchs from the canonical MAC address to using the
identifier from the Bluetooth stack for better connection tracking.

Bug-AGL: SPEC-2541
Change-Id: I27ad0626248e8dba0cacd65f34843b8eec2ca754
Signed-off-by: Matt Ranostay <matt.ranostay@konsulko.com>