* fix(gltf_auto_export): added fix for correct "deep-copying" of objects & hierarchy so that animated
meshes & nested hierarchies get exported correctly
* test(gltf_auto_export):
* added visual testing to check for overall regression :
* added screenshoting in bevy app
* added visual compare with reference screenshot on python side
* added testing of correct export of animated models
* added testing of correct export of empties
* added testing of correct export of nested hierarchies
* added testing of correct export of blueprints, with & without components etc
* fixes#147
