U device configuration

Ok, I know this is a huge PR, but hear me out, I couldn't do otherwise, since all my changes are closely interrelated. 

I'm not entirely done yet, but this is pretty close to the final result. All there is left to do is to be able to save the page's model. I wanted to ship this as soon as possible, because there's a large number of changes and I don't want the other contributors to work on something that would go against the direction I've taken so far for this.