Remove park seed points or fix them

Parks are usually not given as Points, so either select park [entrances](https://wiki.openstreetmap.org/wiki/Key:entrance) somehow, or better select park areas (=ways, not points), then calculate their centroids for example.

No file or test is named. Start by locating the code that selects park seed points and determine whether it queries point features or park areas. Compare the issue's proposed entrance-based and area-centroid approaches; done means park seeds work for parks represented as areas rather than relying on park points.

Written by the indexing model from the issue text.