Overview maps improved

[klokan]

It would be great to have the ilustration images for individual coordinate systems generated by Mapnik. This way we can visualize more information - such as the central meridian, type of projection, etc.

In ideal world we could then even picking of the coordinates made with OpenLayers V3 and projections applied on the data so that people can interact with a map in the true projection. See: http://rjw57.github.io/proj4webgl/ or http://openlayers.org/en/v3.0.0/examples/sphere-mollweide.html