Provide Dockerfile with GDAL Base Image

[justb4]

Is your feature request related to a problem? Please describe.
Some Stetl apps need the latest/greatest GDAL and PROJ versions. For example NLExtract needs the GDAL/OGR LVBAG Driver which is now under active development. Debian (as Dockerfile is based on) and to some extent Ubuntu usually has older GDAL versions.

Describe the solution you'd like
Derive the Stetl Docker Image from a GDAL Base Image. We can start with separate Stetl Dockerfile.gdal and Image as not to disturb existing Stetl apps. Making a Dockerfile.gdal and tagging like geopython/stetl:latest-gdal,
geopython/stetl:2.1-gdal3.2.2 etc. That way projects can gradually migrate. Finally we should aim for a single Stetl Dockerfile.

The GDAL Docker Images are very cleverly (with staging) built (by the GDAL author) and small, includes Proj , Python bindings and GDAL commandline tools. Also Stetl e.g. GML pipelines can benefit from latest GDAL/OGR (performance) enhancements.

Describe alternatives you've considered
Could have custom GDAL compilation in existing Dockerfile but is a complicated build chain will lead to long build times and maintenance issues.