Fix crashing if creating a DEM layer with no files.

Ensure the layer is realized before accepting updates, as VIK_GTK_WINDOW_FROM_LAYER will fail.

In the DEM case: since there's no files, the thread exits and generates a layer update before the layer is realized.
So it's better not to bother with a thread if there's no files to use.
Fix copy and paste typo in a Windows script.
[DOC] Update map download tool text.

Include the map tile info dialog and show an example image.
[DOC] Add an example screenshot of Viking.

This is the currently first shown one on the SourceForge website.
Import Launchpad translation updates
Document previous translation updates
Releasing Viking 1.4.0