Add documentation contributing information with project specific
recommentations along with some common reST and Sphinx constructs.
Reorganize contributing section to fit this new doc in.
Also
* Cleanup stray file (CODEOWNERS) from when docs were in their own repo.
* Remove licensing footer on generated pages (not really needed).
* Pull replacement strings into substitutions.txt for easier management.
Signed-off-by: David B. Kinder <david.b.kinder@intel.com>
David B. Kinder