[Tails-dev] More Native English doc fixes

I've gone through the changes to the docs since 1.6 (using this modified
version of sajolida's suggested git diff command):

git diff 1.6.. -- wiki/src/\[\^b]\*.{mdwn,html}

and here's a branch with my fixes:
https://gitlab.com/JesseW/tails/commits/doc_fixes3

I'm still waiting on my other doc fix branch to go in, also:

https://gitlab.com/JesseW/tails/commits/add_doc_contrib_info

Jesse