Add tests for correct delete cascade behaviour for all result sets

[SysPete]

We need to have proper tests for delete cascade behaviour and also that leaf rows cannot be deleted for things such as Orderline. Initial tests are being added to the Relationships test role. Please use the list below to mark what is done and add your name to any items you wish to tackle.

• [x] Address
• [ ] Attribute
• [ ] AttributeValue
• [ ] Cart
• [ ] CartProduct
• [ ] Country
• [ ] Inventory
• [ ] MediaDisplay
• [ ] Media
• [ ] MediaProduct
• [ ] MediaType
• [ ] MerchandisingAttribute
• [ ] MerchandisingProduct
• [ ] Message
• [ ] MessageType
• [ ] NavigationAttribute
• [ ] NavigationAttributeValue
• [ ] Navigation
• [ ] NavigationProduct
• [ ] OrderComment
• [ ] Orderline
• [x] OrderlinesShipping
• [ ] Order
• [ ] PaymentOrder
• [ ] Permission
• [ ] PriceModifier
• [ ] ProductAttribute
• [ ] ProductAttributeValue
• [ ] Product
• [ ] ProductReview
• [ ] ProductWithSellingPrice
• [ ] Role
• [ ] Session
• [ ] Setting
• [ ] ShipmentCarrier
• [ ] ShipmentDestination
• [ ] ShipmentMethod
• [x] Shipment
• [ ] ShipmentRate
• [ ] State
• [ ] Tax
• [ ] UserAttribute
• [ ] UserAttributeValue
• [ ] User
• [ ] UserRole
• [ ] ZoneCountry
• [ ] Zone
• [ ] ZoneState