Can't use development without the Ansible Vault password

[benrfairless]

As a very junior developer that is eager to start working on upgrading Right to Know soon, it's proving difficult as I need the Ansible Vault password.

If I don't have it, then it's not possible to spin up the development environment.

It should be possible for volunteers and contributors to work on these projects without needing to rip out all the encrypted bits.

[mlandauer]

After a quick discussion with @jamezpolley there's some stuff in the openaustralia/infrastructure README that needs clarification because right now the lack of it is confusing!