GCE is missing ProviderMetadata and locations needed rework.

This change adds ProviderMetadata, which allows us to properly tag locations of zones. It also uses the built-in location features from jclouds core, which allows you to do things like set the property jclouds.zones to constrain locations.

Not quite ready to merge, as I need to adjust one expect test.
this made me question myself.. until I looked at the json from the server!

```
--snip--
   "status": "UP",
   "zones": [
    "https://www.googleapis.com/compute/v1/projects/jclouds-dev/zones/asia-east1-a",
    "https://www.googleapis.com/compute/v1/projects/jclouds-dev/zones/asia-east1-b",
--snip--
```