Add fixed-ip and floating-ip commands

Adds:
* fixed-ip commands: add, remove
* floating-ip commands: add, create, delete, list, remove
* floating-ip-poo command: list

Also uses NAME_ATTR in the Resource class if present to determine
the attribute to be used for searching in utils.find_resource()

Change-Id: Ifd8fa60f880fc4050dea182ac24553cc2c4bff15
Merge "Add fixed-ip and floating-ip commands"