raster ground overlay

[incanus]

It's not tiles and it's not fill pattern images — it's raster imagery "stuck to" the map surface with a given bounding box, and zooming and shrinking with the map. Think of something like a geo-referenced floor plan drawing on top of the map.

Two stages of iteration here:

• Basic single-res image support which supports a limited zoom range to either side of the 100% raster scale before unacceptable distortion
• Multi-sampled, possibly even tiled imagery so that all zooms look crisp

[jfirebaugh]

Duplicate of #1350.