Add the "Security" config group options.
Summary: Added all the "Security" group options listed in T2255.
Test Plan:
- Looked at all the options.
- Tested validation on security.alternate-file-domain
Reviewers: epriestley, btrahan
Reviewed By: epriestley
CC: aran, Korvin
Maniphest Tasks: T2255
Differential Revision: https://secure.phabricator.com/D4334