Sort options by key on "all config"

Summary: Oops, missed this -- alphabetical is probably a better sort order than by-group-then-by-definition.

Test Plan: Looked at alphabetical options.

Reviewers: codeblock, btrahan

Reviewed By: codeblock

CC: aran

Maniphest Tasks: T2255

Differential Revision: https://secure.phabricator.com/D4474