Remove left-over connection nodes

[Patrick-Nijman]

"When you remove e.g. a weir which functions as an outlet and there is a connection node attached which is not connected to any other element this connection node is not removed. It would be nice to check the connection nodes to which a removed item is connected for other connections and remove the node itself too when no other connections exist"

[Rebecca]

[leendertvanwolfswinkel]

Not sure if this issue still exists tbh

[leendertvanwolfswinkel]

Tested today, issue still exists