Updating the Sphinx docs in preparation for the release. I am going through the docs to make sure that i) there are no problems with the generation of the the Sphinx docs and ii) that our docs are an accurate reflection of the current state of the code. As of this commit, I have made a first pass at everything *except*: * Everything in the docs/source/interactive dir. This corresponds to most of the old IPython docs about the ipython shell. * The sections on the multiengine and task interfaces. Of course, this is just a first pass and we likely have lots more to do, but at least, our documentation exists and is no longer misleading or wrong.