add salt-ssh documentation page to TOC
Fix broken link in 0.16.2 release notes
Remove links to nonexistant pages

Would be good to write these eventually, but for now don't try linking
to them since they do not exist.
Add blank lines before and after 'note' rst directives

This quiets warnings in sphinx when building the docs
Fix more broken links

Two links in doc/ref/states/highstate.rst were broken, resulting in
warnings when running sphinx-build to build the html docs. They were
trying to link within the same page, and the section did not exist,
these sections were probably split off into a separate page
(doc/ref/states/requisites.rst) some time ago and these were never
updated to reflect that.