R1:1b5a276a02d6

Add Differential keyboard shortcuts for "mark done" and "hide/show"

Summary:
Fixes T8130. Allows selected comments to be shown/hidden (with "q") or marked done/not-done (with "w").

(These key selections are because "qwer" are right next to each other on QWERTY keyboards, and now mean "hide, done, edit, reply".)

Also, allow "N" and "P" to do next/previous inline, including hidden inlines. This makes "q" to hide/show a little more powerful and a little easier to undo.

Test Plan: Used "q", "w", "N" and…