nickserv/drop: request confirmation when dropping an account

Drop it ChanServ style, because apparently people keep expecting it to
do the same as RELEASE and GHOST...
Merge pull request #196 from grawity/nickserv-confirm-drop

nickserv/drop: request confirmation when dropping an account
Allow protected or owners to register channels too

In Unreal and InspIRCd, the protected and owner channel status also
confer operator status.  Allow these statuses to register channels as
well.  As only protocols that have these statuses set the status flags
in the chanuser objects, this is safe for any protocol module.

Fixes #188