Capability: Display an image file as a map layer

[Malvoz]

This issue is for discussion of the map viewer capability “Display an image file as a map layer”.

[prushforth]

One use case that is important for my organization currently is to display a georeferenced and orthorectified air photo on a map., like any other feature. It shouldn't require us to have a GIS server, just the appropriate metadata in markup, I think. I believe this relates to this use case, but I would like to talk about what metadata is / should be required, so that we can polyfill this. Such metadata is encoded by GIS software in various ways, and we should have a design for how to encode such metadata as HTML markup for say, the <img> element, I think.