Upgrade AWS Java SDK to support for EMR releases

Java SDK release 1.10.6 introduces support for "emr releases" detailed here:

https://docs.aws.amazon.com/ElasticMapReduce/latest/ReleaseGuide/emr-release-components.html

This changeset introduces the ability to spawn EMR clusters with emr-4.0.0, and also enables creating EMR clusters with Spark preinstalled.

• Added an DSL for adding Applications to JobFlowRequests
• Added a SparkStep dsl + test

Thanks pkallos !

1.2.4.2

Clean up bid pricing

1.2.4.1

basic VPC subnet support

1.2.4

• No-args constructor for creating EMR client using default AWS credentials chain (rayo)

1.2.3

• support for IAM roles (thanks ray!)

spark-plug 1.2.2

• availability zone is now configurable
• separate termination protection and keep-alive settings
• support for EMR tagging