Adding a bunch of CLA/contribution-related docs

These still need another once-over. Some of them may have placeholders
for things like URLs and email addresses which are still pending the
DNS work for stigdb.org.
Add CoC document

Still contains placeholders for some URLs which won't exist until the
website DNS/editing work is done.
More legal doc stuff

* Add privacy policy (for linking from the website)
* Add ToS (ditto)
* Tweak a URL in the CLA Appendix.
Merge remote-tracking branch 'upstream/master'
Add URL to the stigdb repo
Add listserv URL

Now that we have a listserv, replace its URL placeholder w/the actual
URL.
Add missing information

* URLs, email address
Add email address

Tell people where to send their CLA.
Add a contact doc

This is a quick and dirty doc of various contact points for the StigDB
project. I need it for linking to from the website. Plus: we need one
anyway.
Merge pull request #57 from vmbrasseur/master

Adding/editing many documents
Add Nota Bene

Everyone needs a CLA on file before a pull request is accepted.
Merge pull request #58 from vmbrasseur/master

Add Nota Bene
Fix formatting

In the transition from .txt to .md I'd missed some format changes.
Fixed now.
Merge pull request #59 from vmbrasseur/master

Fix formatting
POV doc and associated images
Merge pull request #60 from vmbrasseur/master

POV doc and associated images