Vivo stardog

Looks like the main issue that I was having at the hackathon was that stardog, by default, only queries the default graph when no graphs are specified.  I've changed the config a bit and it now works as intended, as far as I can tell.

You can manage this how you'd like obviously, but if I were you, I'd keep each backend as a separate branch on the main repository, and maybe add some verbiage to the README about this.

Please let me know if you'd like any changes made before merging.

PS: This repository was extremely helpful to me and allowed me to get a running start at the hackathon.  Thanks!