Retrieval of DomainResource should warn/error

Expectation is that DomainResource type should not be retrievable since it is an abstract resource. No warnings/errors encountered with the following CQL:

```cql
library Foo

using FHIR version '4.0.1'

include FHIRHelpers version '4.1.000'

context Patient

define "Bar":
  [DomainResource] // should be marked non-retrievable, should give error/warning in translator
```