Create a linter for correct g-c-j usage

[garrettjonesgoogle]

We should create a linter that can detect usage of google-cloud-java that is problematic. Specifically, some users will want to make sure they don't use any @BetaApi features, so the linter should support detection of that in user code.

[garrettjonesgoogle]

This has been added to our feature backlog: https://github.com/GoogleCloudPlatform/google-cloud-java/wiki/Feature-backlog . This issue will be closed but is linked in the backlog and can continue to be used for comment and discussion.