Add "command" vs "flag" corrector modes and refuse to correct "--start" into "restart"

Summary: Currently, we correct "bin/aphlict --start" into "bin/aphlict restart". When a command starts with "-", don't correct it since it's more far more likely a mistake (intended to be a flag or just not correct usage) than a typo.

Test Plan: Ran "bin/aphlict --start", "bin/aphlict restart", "bin/aphlict restatr".

Reviewers: amckinley

Reviewed By: amckinley

Differential Revision: https://secure.phabricator.com/D19984