This adds supported_features support to obc_driver so driver can
provide this information when connecting.
This is required by PBAP 1.2 (page 48):
'Mandatory if the PSE advertises a PbapSupportedFeatures attribute in
its SDP record, else excluded.'
This simplify target matching to a single place making it easier to add
new targets/profiles.
Matching is done by either friendly name e.g. opp, ftp... or Bluetooth
UUID.
Drivers are probed when a session is established and removed when the
session is destroyed.
