hubFS: THE place for F#

Here's a shape that's like a bowl.  We use it in the later simulation.  Here's the F# code for the surface function and range parameters:

do range := (0.0,2.0)
let surfaceA (x,y) =
  let f u = ((1.0 + cos(2.0 * pi * u)) / 2.0) in
  f x * f y + 1.0;;

ff := fun t (x,y) -> surfaceA (x,y);;