LeaseOrderItems, BookOrdersItems, and ProposeOrderItems all replicate logic when should share it #226

In the FacilityStore and SessionStore, LeaseOrderItems, BookOrderItems, and ProposeOrderItems all replicate logic when should share it.
Furthermore the logic in ProposeOrderItems is directly copied from BookOrderItems and needs to be checked if it is correctly in the context of an OrderProposal instead of an Order.