Support import of department boundaries with Z dimension

[meilinger]

This is more of an annoyance than anything, but it is common to get boundary shapefiles of departments that include a Z dimension. As a workaround at this point, we've either:

1. Been importing the shapefile into QGIS and re-exporting excluding the Z dimension OR
2. Using ogr2ogr -f "ESRI Shapefile" 2d.shp Municipal_Boundary.shp -dim 2 to convert the shapefile to 2D (thanks @garnertb !)

Would be nice to not need to perform either of these steps before uploading a department boundary when given a geometry w/ Z dimension.