Change the message when UNQUIETing users

Changed from "... (%d ban%s removed)." to "... (%d quiet%s removed)."
protocol/inspircd: Fix warnings about ignored login name settings with SASL.

Inspircd's METADATA accountname serves both for bursting existing
account names (netburst and SASL) and setting new ones (from services
only). If atheme is supposed to control account names, it must allow
bursts but not new account names.

Atheme did not distinguish the two types correctly, in particular
detecting SASL logins as new account names.

Tested by Techman.
help/nickserv/acc: Only list ACC 2 if it is possible (ACCESS is loaded).

[ci skip]
Merge pull request #297 from maxanton/master

Change the message when UNQUIETing users
hostserv/offer: refactor and search for pre-existing offers (closes #298)
hostserv/offer: fixes
protocol/ngircd: Reduce useless messages about !channels.

We deliberately ignore !channels in NJOIN; do so in MODE and KICK as well.
hostserv: Fix a format string error.
protocol/ircnet,ngircd: Manually send wallops() to all IRC operators.

The ircnet and ngircd daemons do not provide a WALLOPS-like command that
does not send to normal users (with umode +w set). Therefore, fake it by
sending a private notice to each IRC operator on the network.
Add licensing information to everyone's favourite supermegauseful API module.
operserv/override: Don't crash if memoserv is not loaded.