Beautify chat plugin interface

* Style the forms with the new classes
* Add the use_custom_server checkbox in the creation of a chatroom
* New layout (table w/ collapsable rows) in the chatrooms management page
* Add info box in logs page
`var $this = $(this);` is more common for this (or `element` or `toggler` if you don't like `$this`). At least I'd expect `toggled` to contain a bool, not a jQuery object.