Translate 'heeftBetrekkingOp' to 'ZaakObject' instead of translating is as a role

[MLenterman]

Currently heeftBetrekkingOp is being translated to a rol if the gerelateerde is nps, nnp, ves, oeh or mdw, otherwise we ignore it. heeftBetrekkingOp is not supposed to be a role, but should represent the subject of a case. This could be the above mentioned gerelateerde types, but could also be many other thing such as 'adres', etc.

The correct solution is to translate heeftBetrekkingOp to ZaakObject instead.

TODO: Determine if all objectTypes need to be translated or only a subset of objectTypes.