Add an initial sample based on Apple's own tutorial

So, this is my first sample, creating the same sample as shown in Apple's tutorial of AppKit, doing the layout/event handling through code (I have a version that loads everything from the nib file, but we are missing action handling there).

I'm copying your default nib file for my sample, as I don't make use of it (i.e. setting any value for my objects). Lemme know ;)