Minor changes to the filename structure of PBR materials

In this update, the name structure for individual PBR maps inside a .zip file will change slightly: The image type (JPG or PNG) will be integrated into the file's base name, like this:

Old name	New name
PavingStones036_8K_Color.png	PavingStones036_8K-PNG_Color.png

This change makes the name structure more consistent as it means that all files inside the zip file PavingStones036_8K-PNG.zip will also start their names with the exact same string (PavingStones036_8K-PNG) which makes various automation tasks easier to implement without special handling for filenames.

Developers are encouraged to ensure that the new file names can still be parsed properly. Implementations that merely check for the PBR map using underscores (_) as separators will be unaffected by this change, but implementations with more precise regex matching may need to be adjusted. There may be a brief transition period where both name variants are served by the site, so implementations should accomodate both variants for the time being.