CDK-94. Create CDK runtime convenience Maven dependencies

This is an extension of Ryan's work on https://github.com/kite-sdk/kite/pull/78. See https://issues.cloudera.org/browse/CDK-94

I think I intended this to be a provided dependency, although it doesn't look like it was using the provided scope before it was moved to the recommended section. Avro is always provided, should we move this back to the Hadoop-provided section so users don't get conflicting versions in their classpath?