Image Layer Example
Demonstrate a single non-tiled image as a selectable base layer.
The "City Lights" layer above is created from a single web accessible
image. If you construct it without any resolution related options,
the layer will be given a single resolution based on the extent/size.
Otherwise, it behaves much like a regular layer. This is primarily
intended to be used in an overview map - where another layer type
might not make a good overview.