Subclass or alias the map class

[David Manthey]

Currently, when we create a pixel-space image, we can use util.pixelCoordinateParams to get appropriate values to initialize the map object and the tile layer. As a convenience, if we subclassed map as largeimage or slide or some similar name, we could have this take a width and height and then do the expected thing. Similarly, an image tile layer create on such a subclass of map could default to the preferred wrapping, bounds, etc.

As another subclass of map could be a scene or view or similar name which would default to different interactor options -- this might be nothing more than using an interactor where we pass different defaults.