Automatically join channels when msgs are received / Add custom cookies param / Handle multiple join/parts

[corcoran]

This is a rebase of GermainZ PR with the hash removal removed. The hash removal was causing issues with bouncers or auto-join trying to join say #ChannelName after a pickups restart/crash without a reference to the conversation id since the hash dict is wiped out.

This fixes issues with IRC bouncers like ZNC trying to join saved channels (it joins them all at once using a comma separated list).

Finally there's a new param added for custom cookies. This lets somebody run multiple instances of pickups.

[corcoran]

I can separate this into multiple PRs if desired.