Add image service layers to address #932

[tsutterley]

Queries ESRI Image Service APIs and adds image layers similar to an ImageOverlay. Image Service APIs allow the creation of mosaics with options for pre-defined raster functions, interpolation strategies, band combinations, time ranges, etc.

Additional updates to projections to add EPSG:5936 (Alaska Polar Stereographic) and more EPSG:3031 (Antarctic Polar Stereographic) options

[tsutterley]

~~Still having a little trouble with the python-JS bindings (so I could use another set of eyes). The problems might be from how I tried building my docker container for testing. I am pretty sure the JS parts are working at least at the L.imageServiceLayer() stage~~

[martinRenou]

Thanks I'll try to find time to test this out and review :)

[tsutterley]

Ok! I think this is at a good place for review. I needed to extend from a Layer model versus a RasterLayer model and that fixed my JS-Python binding issues

[s-m-t-c]

The additional Polar projected WMS examples in CustomProjections.ipynb helped resolve an issue I had recently.

[dshean]

Hi all. Wondering about status of this PR. @martinRenou, any other changes required? This functionality will be really useful for interactive mapping applications in the polar regions (increasingly important), and having upstream support will be better than current workarounds. Thanks!

[HaudinFlorence]

Thanks for this PR. This works well (as shown on this video produced with using the example notebook ImageService.ipynb)

[betolink]

This looks neat!! @davidbrochart can you guys take a look and consider a merge?

[betolink]

Is there any particular thing @tsutterley needs for this PR @davidbrochart? I see just one change request but perhaps was already addressed?

[martinRenou]

This looks super nice thank you!