R1:d30cc738477a

Two minor Config sidebar tweaks.

Summary:
- 'Config' -> 'Configuration'
- 'Configuration' -> 'Option Groups'

Test Plan: Looked at /config

Reviewers: epriestley, chad, vrana

Reviewed By: chad

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D4531