display projection type on the output (EPSG:3857)

I had a bit of a headache trying to use QGIS trying to add earth curvature to my exported heightmap, digging into mapzen's website I found that the projection type of the heightmaps is EPSG:3857. I'd recommend including that in the output page UI just so end users can import it correctly into QGIS to work right away without too much searching.