Add accountname support and preserve realhost when using masking

Atheme services no longer use +r to indicate authenticated users,
now the services set the "accountname" metadata. This makes that
account name visible to /iwhois as well as the legacy +r mode.

This commit does not set in-game users account name because those
might not be the same between services and minecraft.

The previous hostmask support was hiding the unmasked hostname from
operators. This change preserves the host/vhost distinction for UID
lines which allows server operators to see hostnames as expected.