Named / Global handlers

[bontaq]

This is one possible solution to the far interaction problem ie you click a button, and you want something to change in a distant component.

The idea is that instead of the handler being anonymous, you can give it a name. Then any events sent to it will also trigger re-renders of anything also below a same-named handler.

I think this one can come quickly after the initial hackage release. There's some interesting things to consider, like where do you set the initial state, how do you track what's "subscribed", things like that.