closes https://github.com/teeworlds/teeworlds/issues/522 but reopens https://github.com/teeworlds/teeworlds/issues/2229 It would be nice to have the sha256 of the map in the demo header to be more save that sliced demos do not get corrupted. Thats why I changed the order to load from downloaded maps first. In case there is a map in maps/ with the wrong hash and a correct one in downloadedmaps/ it will prefer downloaded maps.