Zoom to Rendering Level Button

[hallahan]

When the map is zoomed out, the markers and geometries should not be rendered at a certain zoom threshold. Make sure that things are always not rendered when zoomed out, and add a button to "Zoom In to View Data" button.

cc/ @PaulUithol

[hallahan]

If the user adds a POI, automatically zoom the map into a rendering level to ensure that geometries show up by that action.