Re-formatting and adding Rackspace to Copyright headers

Previously, all work submitted by Rackspace employees were done with
"Copyright OpenStack Foundation" headers. This was done because we were
uncertain about the correct legal solution; since then, we have been
instructed to label all our work with "Rackspace US, Inc." copyrights
instead. This commit does that and reformats the docblock to a more
consistent style. Other PHP projects like Symfony, Composer, Doctrine,
etc. all do this.

Change-Id: I3e03b624d889a7a687ce630feef918ef9a24d015