Switch User::usertype back to an unsigned int.•••Leaving it up to the compiler to set the underlying type of the enum
can result in this being a signed int. This variable will not work
as intended as a 2 bit signed int.
This fixes an issue with the Windows build(s) where a server trying
to link would fail with "Protocol violation: Invalid source".
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.