Add FAQ page to docs

This was added per #7024.
Fix sphinx build error due to no :email: role
Add explanation of difference between cmd.wait and cmd.run
Remove unnecessary period from top-level title
Fix sphinx build error

The '=' for the header did not match the length of the page title.
Update the FAQ

This commit adds new information to the FAQ, as well as switching from
in-depth documentation for a couple topics to linking to this
documtnation on the relevant pages elsewhere in the docs.
Add notes on GitPython issue in salt<=0.16.3
Fix sphinx build warnings (new modules not in toctree)
Tweak wording for FAQ link in docs index
Fix sphinx build warning and move FAQ to root

This fixes a warning from new pages not being in a toctree, as well as
moves the new FAQ page from the /ref dir to the root.
Grammar fix

"How to can get involved" -> "How to get involved"
Fix sphinx build warning

This fixes an invalid path to the master_tops docs index page.
Merge pull request #7075 from terminalmage/docs

A bunch of docs commits