[GREENFOOT-264] File open doesn't show gfar files

The gallery now exports .gfar files. On Linux, I saved a .gfar to disk, but when I go to open it from Greenfoot->choose a scenario, it only shows .jar files (despite claiming to be showing "All Files" in the file filter). It would be good if it also showed .gfar files.

Issue metadata

Issue type: Bug
Priority: Lowest
Fix versions: 2.0