Consider supporting nullable complex typed properties

[Proposal is to clarify in URL Conventions and [Core] , as appropriate, that we have null propagation rather than null reference exception semantics.] The same rules apply as for referencing a navigation property with target cardinality 0..1. Example: Companies(1)/HeadquarterAddress/Street will show similar behavior if modeled with a nullable property HeadquarterAddress of complex type Address or an optional navigation property HeadquarterAddress targeting an Address entity with some artificial key. Accepted: https://www.oasis-open.org/apps/org/workgroup/odata/download.php/47722/latest/odata-meeting-18_on-20121213-minutes.html