Create entity properties for orders in line items

We need an order_id & order property in line items entity. For this, we need these tasks completed:

- Add an order_id column in line_items table.
- Add order_id and order properties to the line items entity.
- Make sure that the add to cart logic adds the order id to the line item table, both in user and in manager screens.
- Check if line items recursively load orders
- Views integration, which means a relationship between line items and orders.
- Test rules integration