Add list command

The number of channels to be listed is limited because client-side javascript, also because no one would read 38000 channels (freenode count).

Will work with bitlbee when https://github.com/martynsmith/node-irc/pull/210 gets merged.

The choice of the listeners to be used was made due to many not performant tries on my netbook, subway would crash, etc...

Fix #272, #196