Automatically create titan backends

This PR removes the hardcoded databases and replaces them with ones that can be dynamically created. By default we create local bdb graphs with embedded elasticsearch. We support hbase tables and external elasticsearch by running dendrite in production mode with `mvn tomcat7:run -Dspring.profiles.active=prod`.

There are two issues at the moment with this series:

* Faunus jobs no longer finish successfully for me. The titan job runs fine though. I'm investigating why.
* There is a lot of overhead in using `TitanFactory.open(...)`. We may be able to speed up that call if we can cache connections to elasticsearch/hbase.