Update geocode conversion

[JoostProRail]

There now exists a layer with both spoortakken and geocode information in it; this can be used as a replacement for the current xy_to_geocode api calls. Gathering this layer and interpolating based on the information in here would therefore be a more efficient way to get geocodes for a lot of coordinates.
Some effort in this direction was already done by the beeldherkenning configuratie team. They pointed out that one fix would be is to use the geocode information (stored in the M (measurement) value in the featureserver can overwrite the Z-value in the data (which is not that useful), from where it can be used to interpolate along the linestrings.

https://mapservices.prorail.nl/arcgis/rest/services/Geleidingssysteem_010/FeatureServer/34

[JoostProRail]

Fixed in #49