Preliminary Addition of CosmoSim Simulation Database Query Tool

This it my first pull request of the addition of simulation datbase query tools to astroquery. As it stands, things are in rough shape, but I welcome all comments, concerns, and tips. Thanks!
Here and in other places, you need the # of dashes to match the # of characters:
https://travis-ci.org/astropy/astroquery/jobs/33199693#L1160