CDK-474: CrunchDatasets by URI

This pull request builds on https://github.com/kite-sdk/kite/pull/98 adding changes to get Crunch sources and targets by URI.
Rather than instantiating the view here, I think you should just pass it to the [`DatasetSourceTarget` constructor](https://github.com/ben-roling/kite/blob/CDK-474-CrunchDatasets-by-uri/kite-data/kite-data-crunch/src/main/java/org/kitesdk/data/crunch/DatasetSourceTarget.java#L79). That way we keep the number of places where views are instantiated to a minimum because we always want to push that as late as possible. For example, support for `handleExisting` will probably push that until when the job is being committed.