OLTU-118 - Implement JWS of the JOSE working group

dropped unused Header#Builder inner class

git-svn-id: https://svn.apache.org/repos/asf/oltu/trunk@1524413 13f79535-47bb-0310-9956-ffa450edef68
OLTU-118 - Implement JWS of the JOSE working group

removed unused imports

git-svn-id: https://svn.apache.org/repos/asf/oltu/trunk@1524414 13f79535-47bb-0310-9956-ffa450edef68