trivial: improved toString() representation

git-svn-id: https://svn.apache.org/repos/asf/oltu/trunk@1524736 13f79535-47bb-0310-9956-ffa450edef68
OLTU-118 - Implement JWS of the JOSE working group

added a shortcut method to verify current JWS

git-svn-id: https://svn.apache.org/repos/asf/oltu/trunk@1524737 13f79535-47bb-0310-9956-ffa450edef68