Consider adding a map bounds to prevent the map from moving outside the AOI

[BobTorgerson]

We should consider adding a map boundary that will not allow the user to drag the map outside of that boundary. In Leaflet, this will pop the user back to closest bound of the boundary with a fly-by motion.

This will also help to prevent a bug that I found where you can cause the map to lock up and become unusable.

STR:

1. Scroll the map outside of the bounds of where the map is shown.
2. Click anywhere in the white void.
3. Nothing ever returns.
4. Click Go back to map
5. Try to drag the map back to where there is data available.

[BobTorgerson]

This is for the HSIA map.