FELIX-3935 - Testcases for JAAS integration

Adding testcases for following authentication scenarios
-- With TCCL switch
-- With Felix JAAS related classes on bootclasspath
-- With LoginContextFactory

Removing JaasConstants class from API for now as these constants are only required by testcases

git-svn-id: https://svn.apache.org/repos/asf/felix/trunk@1458707 13f79535-47bb-0310-9956-ffa450edef68