New SUI docs

I rewrote the UI docs to explain things a little better and to give a quick overview of how things are structured as well as point people towards certain parts of the codebase.

Since people will want to develop on their local machines (I miss the QA SingularityService), I also mentioned how they can connect to the Vagrant service.

I also took out the non-proxy ways of getting around the cross-domain restrictions as I felt they were too much hassle. I expanded a little on @timmfin's mention of vee.

/cc @timmfin @tpetr @wsorenson @gchomatas