Add easy DataSet.add_geom

[Permafacture]

let the OGRGeometry object say if it is a line, ploygon or multipolygon. However, markers have more data kwargs so I don't know if it makes sense to allow the kwargs even if they have to be thrown away (geom turns out to be a line instead of a marker), throw an error, or just not let add_geom add markers to avoid confusion.

[Permafacture]

Also, geoms have latlon switched up from how I otherwise add lat lon pairs