* providers/google: Add google_compute_image resource
This change introduces the google_compute_image resource, which allows
Terraform users to create a bootable VM image from a raw disk tarball
stored in Google Cloud Storage. The google_compute_image resource
may be referenced as a boot image for a google_compute_instance.
* providers/google: Support family property in google_compute_image
* provider/google: Idiomatic checking for presence of config val
* vendor: Update Google client libraries
