Implemented headers in Mock servlet request to make testing easier

git-svn-id: https://svn.apache.org/repos/asf/wookie/trunk@1569531 13f79535-47bb-0310-9956-ffa450edef68
Added a helper for making signed requests from functional tests

git-svn-id: https://svn.apache.org/repos/asf/wookie/trunk@1569532 13f79535-47bb-0310-9956-ffa450edef68