Summary: Ref T2255. Ref T2221. Lay the groundwork to move configuration into PHP, so we can show descriptions in the web UI, do typechecking, disable application options when an application is uninstalled, etc.
Test Plan:
{F28421}
{F28420}
{F28422}
Reviewers: codeblock, btrahan, vrana
Reviewed By: codeblock
CC: aran
Maniphest Tasks: T2221, T2255
Differential Revision: https://secure.phabricator.com/D4306
