Hide/toggle POIs and areas.

The map allows you to place points (PoIs) and circles (areas) on the map. However, you can't temporarily hide them - only clear all of them. 

Sometimes, the operator wants to see a clean version of the map to better control the Rover. 

- [ ] Add a toggle to the map server to hide or show points of interest on the map.

## Resources

- POI stands for "Point of Interest"