Add in/out path configuration via environment variables

[DannyBen]

• COMPLETELY_CONFIG_PATH env var can be used wherever a CONFIG_PATH argument is needed.
• COMPLETELY_SCRIPT_PATH env var can be used wherever a SCRIPT_PATH argument is needed.
• Output filename will default to the same name as the input filename, instead of always defaulting to completely.bash
• The output template was adjusted a little more, with some more line breaks for air.