Add a preferences window

Nothing to show there yet.

Coming Soon!
Add list of saved IRC servers in tableview

Creating a NSTableView programmatically is a PITA. If you do it via
interface builder, then IB will do a lot of the heavy lifting for you
(e.g.: creating a scrollview, adding the tableview as a document view,
and adding a single NSTableColumn to the tableview).
Preferences shows all server fields

* hostname
* port
* ssl
* username
* password

Needs some better layout, the ability to edit fields, a split view that
also shows the channels, bindings so that edits here will affect the
current state, etc.