Updates for Latest Blueprints Interfaces

For my Fabric/RexConnect projects, I wanted to try/test the latest RexPro changes with my existing Titan setup. However, Titan wouldn't compile with the latest Blueprints/Rexster. Starting from the `standard-index-experimentation` branch (seemed like the best option), I implemented the changes shown here.

I'm not sure if these changes will be useful/helpful for Titan dev, but I thought I'd share them. Perhaps it would make a decent starting point for the upgrade/refactor to the latest Blueprints. Titan will compile with these changes, although I had to omit `titan-tests` from `pom.xml` to accomplish this -- it has a variety of build failures that would require more extensive code changes to resolve.

This build of Titan executes fine for me locally, and RexPro/RexConnect are working as expected. It also passes my entire suite of Fabric integration tests, which include a variety of index scenarios (both "standard" and with ElasticSearch).