Auto-zoom behavior

There were some issues on diydrones about default zoom behavior. At the moment I think it autozooms to a region when there are three waypoints, but keeps doing that for several interactions.
In my case I tried to plan a very small area but in certain interactions the app decided that a different zoom level would be better for me. In this area I just wanted some more accuracy and I had to zoom back in to get the view I wanted. So I had to fight this, move the map back, zoom back in and place another point. This is cumbersome.
I suggest that the app shouldn't rezoom areas even if some points are temporarily out-of-view, certainly not during planning. Instead a button could be useful to get an overview, after which it's easier to slide the map around and verify placements. ( a button with a square and arrows indicating diagonally outwards could be an icon for this ).

No file, test, or entry point is named. Start by locating the map-planning interaction code and trace when automatic zoom is triggered after waypoint changes. Done means planning no longer unexpectedly re-zooms the map, while any proposed overview control has defined behavior and coverage.

Written by the indexing model from the issue text.