Data export add metadata and lengths

[mszell]

After it is a geojson, add:

• seed points grid
• seed points rail
• city boundary
• length with overlap
• length without overlap
• cumulative length with overlap
• cumulative length without overlap

[mszell]

Make it a parameter whether overlap measures and geometries are exported, only non-overlap measures and diff geometries, or both.

[mszell]

Later with lib this might become some yml or so

[mszell]

First 3 points resolved via #100, rest is still to do.