Changes based on review comments, including:
- Updating to use latest 0.5.0 APIs
- Adding general Zookeeper entity interface
- Make KafkaCluster implement Group
Added EC2 live test for KafkaCluster
Tidy up the Entities class
- Rename supplier to attributeSupplier
- Add newDownloader method to get DownloadResolver for a driver
- Better javadoc
Tidy up the Exceptions class
- Better javadoc
- Unwrap ExecutionExceptions
Use new method in Entities class to get download resolver