[WIP] SciDB backend

This isn't ready to merge, but I've started playing around with connecting SciDB to blaze.

There are two failing tests currently (I think one is a backend bug, and one is a SciDB bug). I also want to add some more tests to make sure I understand how blaze is working.
It's a placeholder for now in case there are some blaze operator names that don't have the same name in SciDB (on my todo list for this PR is compare both systems' operator sets for name differences)