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
This isn't quite correct. The update should be applied to the original dataset, which is identified by the URI "dataset:hive?dataset=products". You don't need to create a new dataset, and the update should be:

```java
Datasets.update("dataset:hive?dataset=products", descriptor2);
```

I don't think there is a need to use the 3-argument version (with `Record.class`).