BUGFIX: bb restart would error when not root and specifying to be a user/group, now check occurs to see if we are already that user/group.
ADDED: ExitCode parameter to Script.ExitError()
CHANGE: All commands run through static methods of a new class Commands
CHANGE: All Script.ExitError() calls updated with os.EX_* codes.
CHANGE: RuleSet() will now silently store exceptions so that various callers can handle those exceptions gracefully themselves, rather than abort the rule loading process.
ADDED: Implementation for 'bb lint'