Small ZNC tweaks

As per #320, here's some very small tweaks to make connecting to a ZNC server a little bit easier. This adds a new "bouncer mode", which displays an additional "Network" input field. When enabled, this sets the password based on ZNC's password format ("username/network:password").

I found it interesting that the code in serverselect.js appears to be using some bits of Backbone, but not its model binding functionality. Is there a reason for this?