WIP: Rackconnect v3 Load Balancer Pool support

This provides API support for RackConnect V3 load balancers.  First task of #104 
I had to read this a few times and nearly thought I totally screwed up RCv3 ;) My brain parsed "instance" as "a Cloud Server", not "an instance of a class"; so it read as "there is a difference between the Nova id and this value". I think it may be useful to move the parenthetical to its own sentence, and clarify that this is distinct from the ``id`` attribute (eliding "instance"), because that is RCv3-specific, whereas this is really the Nova id.

Does that make any sense?