basic off-channel support; restructuring how part functions are handled

* added srvx.conf setting to allow chanserv to work being outside of a channel; if you'd like to have srvx set a mode as it joins, edit REGISTERED_MODE in hash.h. this will not work properly on P10 networks - though it may be nice for bahamut-based networks. either way, please do not ask us for assistance.

* changed the way part functions are called - a modeNode is now passed, and they are run *before* the user's membership link in that channel is nuked.

git-archimport-id: srvx@srvx.net--2004-srvx/srvx--devo--1.3--patch-58