v1beta16 api support

* v1beta16 introduces a new quota structure that has the following changes:
  * All zone quotas have been removed and will no longer be enforced or reported.
  * Regional resources now have quota information and take the place of old zone quotas.
  * Certain global quotas have been removed or migrated to become regional quotas.
* Added support for GCE regions
  * `knife google region list`
* Added support for GCE projects
  * `knife google project list`
* Added service account scope support when creating new servers.
* Update UA string to `knife-google-v1beta16`
* Bumped knife-google version to 1.2.0