Screen; added bounds; changed w/h types, tidy up - see extended description
Screen; added bounds; changed w/h types, tidy up - see extended description

    - changed `w` and `h` to `Int` type
    - added `width` and `height` to `Float` if needed
    - removed redundant cache values and error prone sync code
    - added `bounds` getter, returns a `luxe.Rectangle` for convenience
    - clarified that `mid`, `size`, `bounds` will return _new_ instances
        - this is because cached values get modified by user code
        - immutability is in the new vector code for later alpha

zollenz/luxe,anissen/luxe,FuzzyWuzzie/luxe,NicoM1/luxe,kevinresol/luxe,tnRaro/luxe,underscorediscovery/luxe,zollenz/luxe,mrcdk/luxe,FuzzyWuzzie/luxe,josuigoa/luxe,mrcdk/luxe,underscorediscovery/luxe,anissen/luxe,tnRaro/luxe,thecocce/luxe,NicoM1/luxe,jeremyfa/luxe,jeremyfa/luxe,thecocce/luxe,kevinresol/luxe,josuigoa/luxe