also made all other exporters do this.
Made some internal changes.
- moved path functions from bpy.utils to bpy.path (similar to os.path)
- added functions...
bpy.path.ensure_ext(path, ".ext", case_sensitive=False) # simple function to ensure the extension is set.
bpy.path.resolve_ncase(path) # useful for importing scenes made on windows where the path case doesnt match the files.