Allow GeoTIFF-based visualizations in data set restriction

[dokempf]

The satellite map is not useful for very fine-grained control. Instead, hillshade and slopemap based visualization should be plugged into ipyleaflet. This should probably wait for refactorings that come out of #70

[mariashinoto]

GeoJPEG may be important as well.

After all, I received more GeoJPEGs from Michael than GeoTIFFs, so it may be an equally important format.

[dokempf]

#87 was a substantial step towards completing this issue. What remains is to integrate the advanced map features into DataSet.restrict.

[dokempf]

The refactoring of rasterization and visualization was finished in #97, so this could now be tackled @GwydionJon