Provide way to center map on visible points

[saylorsd]

Currently when a visitor searches, the points the map are filtered on that search. This often leads to the current map view becoming completely empty.

I suggest we provide a button to center the map on the visible points. And maybe have a toggle that, when on, will signal the map to recenter on the visible points as the user searches.

Since we're getting paginated results, we'll might have to use the bounding box of the current page which likely is far from random, especially geographically-speaking.

I'll look into whether we can return the bounding box for all valid assets on a search while only providing the details for the few in the list.