Allow AWS_PRIVATE.. credentials to be defined through environment variables too.
Allow AWS_PRIVATE.. credentials to be defined through environment variables too.

Supports:
- AWS_PRIVATE_S3_ACCESS_KEY_ID / AWS_PRIVATE_ACCESS_KEY_ID / AWS_S3_ACCESS_KEY_ID / AWS_ACCESS_KEY_ID
- AWS_PRIVATE_S3_SECRET_ACCESS_KEY / AWS_PRIVATE_SECRET_ACCESS_KEY / AWS_S3_SECRET_ACCESS_KEY / AWS_SECRET_ACCESS_KEY

edoburu/django-private-storage