fix build name ConfigTemplate processing [GH-858]

Addresses issue with build name ConfigTemplate processing causes errors with `-only` and `-except` command line flags, and with post-processor and provisioner only and except attributes.

The approach allows backwards compatibility with anyone using a build name template string (e.g., `{{user "foo"}}`) in `-only` or `-except` command line calls.

Also, added tests to verify behavior in the command line, provisioner definition, and post-processor definition.

I'd appreciate a head-nod that this looks good from another committer.

/cc @strcrzy