[google|compute] Complete Operations support

- Add missing Operation attributes
- Remove unnecessary attribute aliases
- Add "zone_name" attibute for backward compatibility
- Add "destroy" method for an Operation
- Add "all" method for Operations
- Fix a bug when building an empty response (ie on delete operations)
- Return nil on NotFound Operations (behave like other fog resources)
[google|compute] Modify Snapshots

- Add missing "Snapshot" properties
- Fix "delete" request, as "Snapshots" doesn't require a zone
- Added "destroy" and "ready?" methods to model
- Removed "project" param
- Removed custom "reload" method in favour of the standard fog method
Merge pull request #2839 from frodenas/gce_operations

[google|compute] Complete Operations support
Merge pull request #2848 from frodenas/gce_snapshots

[google|compute] Modify Snapshots
[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