[ADD] Combined Backend conisting of two layers of backends, bdb and jclouds, neither tested nor functional at the moment

git-svn-id: https://svn.uni-konstanz.de/disy/Treetank/trunk/treetank@7268 e3ddb328-5bfe-0310-b762-aafcbcbd2528
Merge remote-tracking branch 'refs/remotes/git-svn'