Update Settings to use full side-navigation
Summary: Moves Settings to use a normal side navigation vs. a two column side navigation. It also updates Edit Engine to do the same, but I don't think there are other callsites. Added a consistent header for better clarification if you were editng your settings, global settings, or a bot's settings.
Test Plan: Test each page on a personal account, create global settings, test each page there, create a bot account, and test each page on the bot account. Anything else?
Reviewed By: epriestley
Differential Revision: https://secure.phabricator.com/D18342