add recenter and scrollbar for quick scaling to Map (editor)

[Mariusthvdb]

consider the above zone in Solo Indonesia, and notice there is neither a scrollbar, nor a recenter button available.

All I can do to go back to my original Map is click the - button 20 times.

also note there is no way to get back to the main Zones list at config/zone, which would typically be the thing to do after editing an individual zone.

please consider adding these tools to facilitate Zone editing

• scrollbar
• recenter button
• button to go to config/zone