Consolidate DataResource and DatastoreResource

[dafeder]

In order to eventually sort our our circular dependency issues and get the DKAN modules organized in a more intuitive way (not to mention making the code more comprehensible) we need to collapse these two very redundant classes/objects into a single thing. The DatastoreResource class has very little value; it does not reference any other classes or services from the Datastore module and just adds a few more properties that are just built from the DataResource properties.

This will take a bit of trial and error to get right, but will consist of, generally

1. Figuring out how to reproduce any additional fuctionality from DatastoreResource in the DataResource class. This may involve some util-type functions that stay in Datastore and process info retrievevd from DataResource`.
2. Changing all uses of DatastoreResource throughout the Datastore module to use DataResource instead.
3. Deprecating DatastoreResource but keeping for now as a shim to prevent any custom or contrib code using it from breaking.