t2337: initial sphinx project for kickstart docs

* use the oms theme in oms-doc-themes
* this includes the Makefile and conf.py from oms-docs, modified
  slightly to work here with the theme directory external to the
  repo here.
* basic .rst for index, intro, getting started, general use, and
  contributing, along with a TOC.
* update .gitignore to drop _build
* include requirements.txt to define python packages to install