CDK-469: Use schema URIs in create command

This updates the create command to pass Schema URIs to DatasetDescriptor, which will set them using the URI option for Hive tables and avoid [CDK-469](https://issues.cloudera.org/browse/CDK-469) for schemas longer than 4k.
Is this a standard URI scheme? Howe about just looking for the resource on the filesystem, then falling back to the classpath? This is what we do in the Maven plugin: https://github.com/kite-sdk/kite/blob/master/kite-maven-plugin/src/main/java/org/kitesdk/maven/plugins/AbstractDatasetMojo.java#L119