Currently only one GPX track, Umap and POI file can be added to render on top, change this to a list of type / filename pairs of arbitrary length, or even just a list of file names with format auto detection.
[x] add import_files list to RenderingConfiguration settings
[x] add legacy gpx_file, umap_file and poi_file entries to import_files list (avoiding duplicates)
[x] add command line support for multiple files in render.py
Currently only one GPX track, Umap and POI file can be added to render on top, change this to a list of type / filename pairs of arbitrary length, or even just a list of file names with format auto detection.