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 dataset is essentially the same as a table in a database.

I don't think we should say this. It leads to questions about what the difference actually is and why Kite doesn't work like a database. Instead, we should say that it is like a table and is a collection of records. Records are like table rows, but they can store nested structures like lists, maps, and other records.