Add even more Differential options

Summary:
These are technically in MetaMTA right now, but I put them in Differential since I think it's probably a better primary category fit and having 120 options in MetaMTA won't do anyone any favors. (We can do some kind of cross-categorization or "related options" later if we get feedback that people are having trouble finding options like these which have multiple reasonable categories.)

Also improve the readability of displayed JSON literals with forward slashes.

Test Plan: Looked at options, edited a couple of them. Looked at JSON literal values, saw them rendered more readably.

Reviewers: codeblock, btrahan

Reviewed By: codeblock

CC: aran

Maniphest Tasks: T2255

Differential Revision: https://secure.phabricator.com/D4464