OAK-2051 - Provide option to use Configuration SPI in JAAS authentication when running within AppServer
OAK-1880 - Omit Configuration Retrieval for PreAuthContext

Merging 1601578,1620512. Also includes OAK-1880 as related changes were required



git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/branches/1.0@1620786 13f79535-47bb-0310-9956-ffa450edef68