Adhere to the maximum line length for YAML adopted by CFN

[villasv]

Uploading the code to the designer and then downloading it will convert a vew string blocks from standard line continuation | to >, introducing a bunch of blank lines. This is a minor inconvenience, the changes are rapidly undone.

A very minor issue, but making the upload/download idempotent would be pretty convenient.

[villasv]

Particularly complicated for sections about files instead of commands. Airflow celery config vars are almost already 50 chars long... abuse Fn:Sub?

[villasv]

Will also be facilitated by #34 if we remove those long scripts from the YAML file

[villasv]

Not completely done, but it's pretty consistent now except for the environment variables section.