CDK-140: Add namespaces

I spent some time trying to implement this and it ends up requiring a few special cases because we don't have a way to pass general URI options to the `DatasetRepository#create` method. I added the ability for the repository builder to request a location, but that led to problems reconstructing the URI. I suggest we leave it as-is for now and add the ability to override the path namespace and dataset name in the future when it is requested by a customer.

Is that reasonable?