Our admin settings forms consisted of a mix of new and very old code,

and because of this we had inconsistencies in how some styling and logic

was done. In order to help future-proof things, to help others work on

settings code in a consistent form, and to generally clean up the

codebase, this change updates all of the code to better fit our modern

code and doc standards.
While mostly centered around adding docs and moving from double quotes

to single quotes, this also moves some forms to module-level logging,

updates a URL to the Review Board support settings page, localizes some

strings, moves a complex call to send_mail to use keyword instead of

positional arguments, and improves a check in the SSH settings form.

Unit tests pass.
Went through each form and tested them.