Add connector name option

Add connector name option

Refer to connectors by their human-friendly names in lease
configuration.  The default 1 connector / lease configuration
will continue to use lists of connector_ids to avoid
unnecessary string conversions.

Connector names take precendence over connector_ids in the
configuration.  i.e. if connector names are present all
connector_id values are ignored.

Bug-AGL: SPEC-3815

Change-Id: Idb14c1b6ccc68e327d2d154aac48b44d0c6022a8
Signed-off-by: Damian Hobson-Garcia <dhobsong@igel.co.jp>