Rigify: finish clearing out warnings in functional code.

rigify/__init__.py

rigify/base_rig.py

rigify/feature_set_list.py

rigify/metarig_menu.py

rigify/operators/__init__.py

rigify/operators/action_layers.py

rigify/operators/copy_mirror_parameters.py

rigify/operators/generic_ui_list.py

rigify/operators/upgrade_face.py

rigify/rig_lists.py

rigify/rot_mode.py

rigify/ui.py

rigify/utils/misc.py

rigify/utils/rig.py