Fix DNSBL connect class matching.•••A user that is not marked by a DNSBL should never match a
class that requires a DNSBL marking.
Thanks to @kylef for reporting this on IRC.
Minor cleanup and documentation improvements.•••- Only show a generic failure message to the user upon oper failure
due to not having a secure connection or matching cert. fingerprint.
- Update the comment about oper:fingerprint as it can be a space
separated list of fingerprints and not just one.
- Improve a few code comments and formatting.