File headers: use SPDX license identifiers

add_camera_rigs/__init__.py

add_camera_rigs/build_rigs.py

add_camera_rigs/composition_guides_menu.py

add_camera_rigs/create_widgets.py

add_camera_rigs/operators.py

add_camera_rigs/prefs.py

add_camera_rigs/ui_panels.py

add_curve_extra_objects/__init__.py

add_curve_extra_objects/add_curve_aceous_galore.py

add_curve_extra_objects/add_curve_simple.py

add_curve_extra_objects/add_curve_spirofit_bouncespline.py

add_curve_extra_objects/add_curve_torus_knots.py

add_curve_extra_objects/add_surface_plane_cone.py

add_curve_extra_objects/beveltaper_curve.py

add_curve_ivygen.py

add_curve_sapling/__init__.py

add_curve_sapling/utils.py

add_mesh_BoltFactory/Boltfactory.py

add_mesh_BoltFactory/__init__.py

add_mesh_BoltFactory/createMesh.py