Allow the creation of two map views

[michael2402]

The main goal of this ticket is to allow the creation and use of two map views. It is a central place to collect things preventing us from using multiple map views.

So far, those are the main problems for displaying the same layers twice:

• Main.map.mapView.repaint() or Main.map.repaint() calls. They can be traced using the --trace option. The stach trace triggering such a repaint will be dumped. Layers should simply invalidate their layer. Use #12654
  • undo does not trigger a layer invalidated
• Layer.isChanged() cannot be used with multiple map views. Map view needs to track changes by itself using the invalidation events
• AbstractTileSourceLayer needs to be changed to use one TileSet per MapView.

Displaying different layers:

• The layer list is already prepared to work with multiple layer managers.
• Many layers assume they are only added/removed once to a layer manager (AbstractTileSourceLayer, ValidatorLayer, MarkerLayer, ...). #12872 might solve this for implicitly added layers.

Editing in the second view will be much harder, because:

• MapModes assume there is only one map view

This works:

• Creating a second MapView
• Moving and zooming the map
• Display a data layer
• Display selection