[google|compute] Add Firewalls support

- Add "Firewalls" model and collection
- Modify "insert" method to add "description" and "targetTags" properties
- Modify "insert" method to not prepend network URI if is set by user
[google|compute] Add Addresses support

- Add "Addresses" model and collection
- Add "list_aggregated_addresses" request
- Modify "insert" request to allow "description" property
Fix build broken by 96a56b954eec6c2e93e0b9f696bed08c8414d1d7
Merge pull request #2840 from frodenas/gce_firewalls

[google|compute] Add Firewalls support
[google|compute] Also tweak default disk in tests
Merge pull request #2846 from frodenas/gce_addresses

[google|compute] Add Addresses support
Merge branch 'master' of github.com:fog/fog
Fix Disk tests
Lists disks isn't a valid test since response varies greatly by disk.
Merge pull request #2849 from icco/master

Fix bugs in disk tests
[google|compute] Add Networks support

- Add "Networks" model and collection
- Modify "insert" request to allow "description" and "gatewayIPv4" properties