Rigify 0.5 metarig fixes, advanced generation options, code cleanup

rigify/__init__.py

rigify/generate.py

rigify/metarig_menu.py

rigify/metarigs/Animals/__init__.py

rigify/metarigs/Animals/bird.py

rigify/metarigs/Animals/cat.py

rigify/metarigs/Animals/horse.py

rigify/metarigs/Animals/shark.py

rigify/metarigs/Animals/wolf.py

rigify/metarigs/Basic/basic_human.py

rigify/metarigs/Basic/basic_quadruped.py

rigify/metarigs/human.py

rigify/rigs/faces/super_face.py

rigify/rigs/limbs/arm.py

rigify/rigs/limbs/leg.py

rigify/rigs/limbs/paw.py

rigify/rigs/limbs/rear_paw.py

rigify/ui.py

rigify/utils.py