Allow downloading maps by zooming into or clicking on a non-downloaded region

[PureTryOut]

OSMand does this on Android and that works really well imo. Basically you zoom into or click on a map area that you don't have and a simple menu comes up indicating what map region that is, how large the download will be and a button to confirm the download. That would especially be nice if at some point the map download options get split up into per province downloads, as right now you can only download whole countries at once it seems.