CDK-529, CDK-530: minor API updates from examples

This implements CDK-529 and CDK-530 (to avoid merging two requests).

* Add `Datasets` methods without type argument that use `GenericData.Record`
* Deprecate `CrunchDatasets.asSource(View, Class)`
This looks like a bad docs change, but it's a diff artifact. The method was added and the "URI string" doc matches the argument. The reason the diff happened this way is that the next `update` method's doc had a copy error and used "create" instead of "update".