Fix/aws secrets manager through container

[vymao]

Right now, the secrets decorator injects the secrets into an AWS Batch job after the container has been set up. However, there may be times when secrets are necessary at the container setup entrypoint. This PR allows a user to specify a name and secrets ARN so that these can be passed into the job configuration at construction time in the form of {"name": NAME, "value_from": SECRETS_ARN}, so that the right fields can be set like in the AWS documentation.

[savingoyal]

@saikonen reminder for review. @vymao can you rebase on top of head of master?