Re-allow CustomAggregate and ApplySupported targeting EntityType

[ralfhandl]

At SAP, entity types carrying these annotations are not re-used across containers, therefore annotating the types directly is sufficient and simpler.

The alternatives (targeting EntitySets and Collections) would remain valid.

Proposal

Addition to the Core.AppliesViaContainer tag:

Servers that apply the tagged term based solely on the entity type, structural or navigation property, independently of the container MAY additionally annotate the EntityType, Property or NavigationProperty model element in order to facilitate the annotation consumption by OData clients.

See also PR #137.

After reopening, see also PR #153.

Imported from ODATA-1448