L7 rebased

Adds coverage of the TargetHttpProxyApi, UrlMapApi, GlobalForwardingRuleApi, and BackendServiceApi.

Also adds a complete License file to the top level.

I apologize for the large size of this PR.
This comment was from the original committer. 

@adriancole As it is right now if it is a POST request we are providing compute scope by default (right?) so this should be fine without special-casing?