Reviewer: mirw - ccstor44 changes

I've added a full tree URL (w/ commit ID) to the changelog. I also added examples of the requisite commands for checking out the specific tree. This information is available in debian/changelog for Clearwater builds with remote URL format - git@githum.com:Metaswitch

I've also added debian/license that will be appended to debian/copyright for all projects that use this repository to build their debian packages.