Provide a way to re-center the map

**Is your feature request related to a problem? Please describe.**
It is possible to zoom too far out of the map, or shift the map around so that the map nodes are off-screen. In this situation, it would be helpful to have a method of re-centering and zooming the map so that the nodes are back in view.

**Describe the solution you'd like**
Perhaps add a button to re-center the map