extract cassandra configuration in a configuration file

git-svn-id: https://svn.apache.org/repos/asf/archiva/trunk@1582094 13f79535-47bb-0310-9956-ffa450edef68
better with adding the default file...

git-svn-id: https://svn.apache.org/repos/asf/archiva/trunk@1582095 13f79535-47bb-0310-9956-ffa450edef68