Moving Kite Dataset API info from old guide per CDK-753.

Link to the old guide from which this came. This is just shards of information brought forward so they're not lost. This info should be woven into the samples before 1.0.

http://kitesdk.org/docs/current/kite-data/guide.html
> A Kite `Dataset` object defines the fields for a single row in a dataset.

This isn't true. The `Dataset` interface provides methods to work with the collection of records it represents. The one that is relevant for this article is `getDatasetDescriptor`, which should be used to introduce a descriptor and the metadata it encapsulates. Most of the interesting methods are on the `View` interface, which isn't covered here.