scale function and parameter

[corybrunson]

By design, the samplers have no scaling parameters; the only parameters that affect the underlying manifold from which points are sampled have to do with aspect ratios, and aspect ratio parameters that would "preserve" (uniformly scale) areas, e.g. the coordinate radii of an elliptical disk but not those of an ellipse, are excluded.

Yet users may require samples scaled from their implemented sizes. A scale parameter can be passed internally to base::scale() after being ensured to be a numeric vector and to have length either 1 or the number of dimensions of the coordinate space.

[corybrunson]

On reflection, this might be fraught, since in some cases scaling would preserve uniformity in some coordinate directions but not others. Putting this on hold for now.