Separate concerns between metadata extensions and resource types

[roll]

Currently, implementations have only one way to identify a resource type -- checking if profile: tabular-data-resource. But Tabular Data Resource can have a profile set to URL; it also can be set to an extension URL. It makes it basically impossible to guarantee resource's type information communication.

It will be more robust if the metadata enrichment system (profiles/extensions) is not mixed with the logical data structure (text/table/etc) as it is mostly orthogonal. For example, we might have Fiscal Data Resource but it still needs to be a table logically