Add a control to re-center map

[alexboia]

Is your feature request related to a problem? Please describe.

If one wanders off exploring the map outside de bounding area of the GPS track, it's sometimes hard to go back to that area.

Describe the solution you'd like

Add a control to the front-end viewer map that allows one to re-center the map to the GPS track bounding area - basically the initial state of the map when it's first loaded.