Changed channel hook names

I'm good at this, aren't I?
Moved function "gmatchpack" into channel module

...because I forgot to do it before.
Split up MODE handler

The MODE command handler now parses the message and checks whether it is
a channel mode or a user mode, and calls the appropriate hook.
Update README
Moved NICK_PREFIXES to channel module file
removeModule now removes cached module too
Fixed module unloading
Added command system to debug MODE handling

test.lua now has a simple command system to aid in making the MODE
handlers work properly. The user mode handler also has a temporary print
to help with this.