Configuration dialog for the Overview Map plugin.
completed by: marthd
It should be possible to customize the overview map using a configuration dialog.
The configuration dialog should provide a
Preview button that triggers a file dialog. The overview map needs to be in 2:1 ratio format (Equirectangular projection).
There should be a size entry where the user can specify the width (height would get specified and displayed automatically next to it to ensure the 2:1 ratio). For input two synchronized spinboxes can be used for width and height or a single slider (with the geometry displayed in a label underneath.
It should be possible to choose the color for the position indicator on the overview map. The selection should be consistent with the coordinate grid and position marker plugin.
Settings should get saved and restored properly.