Todo: fix subcluster list for event-display

[153957]

Currently the subcluster list in code.js is manually entered.
And it excludes all subclusters with one or no stations.

This is because I had trouble with Leaflet showing a map when there was only one coordinate.
Also a problem for enschede. It works, but the map is initially gray, until you zoom. - Fixed in f7787aa

Perhaps also create a clusters.json to dynamically load the appropriate cluster names.