Clarify representation of navigation properties in response that are expanded by $apply

In the context of ODATA-1449 we clarified that if the paths expanded by transformation e.g. transformnested include a navigation property, the resources addressed by that path are included in the output set of the transformation, but that it requires a dedicated $expand of that navigation property to include the resources also in the response to the request.

This is in line with the following para in section 3 System Query Option $apply of the current WD of the spec:: "This means an output set can contain structural and dynamic properties as well as navigation properties, Navigation properties in the result of $apply can be further expanded using $expand (see Evaluating $apply)."

However, transformation groupby behaves differently: Navigation properties part of a grouping property path are returned expanded in the response to the request - see examples in spec text.

This means the specification has two behaviors when processing paths with navigation properties. It should be clarified if this is intended.

In this context, the text at the end of section 3.10.2 should be sharpened. It says: "Grouping properties that specify navigation properties are automatically expanded, and the specified properties of that navigation property correspond to properties specified in a $select expand option on the expanded navigation property. " - It is unclear if it describes the effect for the output set of the groupby transformation or for the response to the request.