Add support for CloudFormation and Packer

This changeset adds support for AWS spot instance cluster spin-up via
CloudFormation and AMI generation with Packer. In addition, AMI
definitions exists for Mesos leaders (Mesos, Zookeeper, HDFS NameNode,
Spark) and Mesos followers (Mesos, HDFS DataNode, Spark).

This changeset also bumps the base Ubuntu distribution for 14.04 and CDH
to 5.