[glesys] ip details should be ip details, not listfree
[glesys] Fix ip model name to match nameing convention

Fog::Glesys::Compute::Ip -> Fog::Compute::Glesys::Ip
[glesys] Fix ip attributes, they didn't work

The attributes didn't match up with Glesys API.
[glesys] Return nil if there isn't any public ip address
[glesys] Refactor the ip interface, did not work earlier

Some requests were ok but they never returned a ip. Now you can
manipulate ips in a whole new way. :sunglasses: