Support for structured types

[rpbouman]

Structured types are not handled well. See for example in https://gegevensmagazijn.tweedekamer.nl/OData/v1

TK.DA.GGM.Models.DataService.MarkeringCT
in

VerslagDraadboekfragmentType
VerslagActiviteitActiviteithoofd
VerslagActiviteithoofdActiviteitdeel

Proposal is for the jubilant meta model to project the properties of the structured type as if they were properties of the entity itself. We will have to mark those as coming from a structured type, since we need to $select the structured type property, not any fields within it. Paradoxically, the syntax

structuredTypePropery/FieldWithinStructuredType

is not valid in the $select, but it is valid in the $orderby and/or $filter.