added addtl constructors for Person, Address, Order, OrderItem & InventoryItem.  I now have a constructor that is designed to be used with the creation of a brand new instance that is not already in the database, which will generate a new Guid.  The other constructor is designed to be used to create/load an instance from the database.  This constructor will not generate a Guid, it will simply load the existing Guid as an argument/parameter.