* Vendor google.golang.org/api/cloudbilling/v1
* providers/google: Add cloudbilling client
* providers/google: google_project supports billing account
This change allows a Terraform user to set and update the billing
account associated with their project.
* providers/google: Testing project billing account
This change adds optional acceptance tests for project billing accounts.
GOOGLE_PROJECT_BILLING_ACCOUNT and GOOGLE_PROJECT_BILLING_ACCOUNT_2
must be set in the environment for the tests to run; otherwise, they
will be skipped.
Also includes a few code cleanups per review.
* providers/google: Improve project billing error message
facc50d308