Added support for ANSIBLE_VAULT_PASSWORD_FILE

[AsharLohmar]

Ported some code from ansible.cli so that the DataLoaders would have access to vault secrets when the ANSIBLE_VAULT_PASSWORD_FILE ENV var is set.
Vault ids are not supported.
The idea was to help with the #115

[ssbarnea]

I converted it to draft due to lack of test coverage.

[AsharLohmar]

It's my first PR so I'm not good with all this stuff.
I've "seen a need" (because I was annoyed by those messages too) and found a "solution", by porting (copying) the code from the ansible cli. Seen that it was a matter of just a few lines of code, I thought that even if this doesn't go through at least maybe someone will find enough to do it properly. That's also the reason I ported the code in the exact same form (as much as possible) as I found it where I found it.