Moved most documentation to doc directory, managed by sphinx

I basically relocated most text files to doc and converted them to rst files. My goal here was not to make things pretty, but rather to make things work. As such:

* I did absolutely 0 theming
* the conf.py is rather standard.
* I didn't touch the man page. While it's possible to generate man page info, I suspect that, given it converts all documentation into man page output, we'd want to selectively choose what should be included instead. Therefore, I've retained the old man page[1].

Once dependencies are installed (Sphinx, latexpdf), you should be able to just `make html`, `make latexpdf`, etc from the doc directory. Though this is obviously incomplete, I thought opening a pull request would allow for discussion. 

* Now that I think about it, I probably need to put that back at the top level, assuming some script expects it to be there in order to correctly install it.