Summary: Ref T11589. Provide a way for scripts to say "just continue if database config fails", and use it in `bin/config` and `bin/storage`.
Test Plan:
- Broke database config.
- Ran `bin/config`, worked fine.
- Ran `bin/storage`, got helpful "set up the database" message.
- Ran `bin/repository`, got fatal.
- Ran normal site with valid/invalid config, got proper feedback.
Reviewers: chad
Reviewed By: chad
Maniphest Tasks: T11589
Differential Revision: https://secure.phabricator.com/D16502
