WIP: Rackconnect v3 Load Balancer Pool support

This provides API support for RackConnect V3 load balancers.  First ask of #104 

UPDATE 11/14:  Magic session reset bug is fixed by #110.  Still missing:

- [ ] Test coverage for bulk add to/delete from MULTIPLE load balancers instead of just one
- [ ] `seconds_to_timestamp` tests
If I understood your comment, if there is a 409 there are no partial adds/deletes.  If so, should this part be in a separate loop?  So if there are any errors, none of the servers get added, and the servers only get added if the list of errors is empty?