Screens supporting CSS and/or CSS_PATH

[lllama]

I associate Screens as almost separate Apps (at least in terms of display) and it is often necessary to give a Screen's widgets some style tweaks. It would be nice to give them their own CSS styles. I suppose I still want the base styles to apply so the selectors would need to be tweaked behind the scenes. E.g.

Static {
    border: solid red;
}

Would become:

MyScreen Static {
    border: solid red;
}