Better formatting
Tidied imports
Better Argument Handling:
- Custom argparse types; csv_list adn csv_dict
- Renamed methods and parameters for better reading
- Added argument descriptions to launch_instance descriptor
Minor style update
Removed references to arg_ vars
Refactored aborts up to the command line script, launch. User data failures (previously the only triggers of abort) now escalate a UserDataError
Updated additional security group argument help
Removed unnecessary config items from userdata template
Switch from manual temp file to NamedTemporaryFile