R1:ec306497f54d

Lock down bot adapter API slightly

Summary:
- Reduce visibiliy of config.
- Add a typehint.

Test Plan: Ran campfire/irc bots and chatted with them.

Reviewers: indiefan

Reviewed By: indiefan

CC: aran, amerigomasini

Differential Revision: https://secure.phabricator.com/D4923