Carve out a separate "Modules/Extensions" section of Config
Ref T13362. Config is currently doing a ton of stuff and fairly overwhelming. Separate out "Modules/Extensions" so it can live in its own section.
(This stuff is mostly useful for development and normal users rarely need to end up here.)
Test Plan: Visited seciton, clicked around. This is just a visual change.
Maniphest Tasks: T13362
Differential Revision: https://secure.phabricator.com/D20930