migrate reg-appspot to argparse and split common options into the appropriate library modules
migrate reg-email to argparse and use common options from library modules
migrate reg-http,url to argparse and use common options from library modules
move common registration options into a new reg module
- this allows to avoid spawning reg-url in reg-appspot
- fix minor typo via pylint
migrate flashproxy-client to argparse and use common options etc