Allow "signatureUser" to be configured instead of "user".


Conflicts:
	systests/ws-security/src/test/resources/org/apache/cxf/systest/ws/action/client/client.xml
	systests/ws-security/src/test/resources/org/apache/cxf/systest/ws/action/server/server.xml

git-svn-id: https://svn.apache.org/repos/asf/cxf/branches/2.7.x-fixes@1524715 13f79535-47bb-0310-9956-ffa450edef68