Configure artifact manager s3

Basic configuration of the Artifact Manager on S3 plugin

sample configuration

unclassified:

artifactManager:

artifactManagerFactories:

- jclouds:

provider: s3

aws:

awsCredentials:

region: "us-east-1"

s3:

container: "${ARTIFACT_MANAGER_S3_BUCKET_NAME}"

prefix: "jenkins_data/"