Improve Deletion of Products

[pozylon]

Removing a product should:

• [ ] Deny removal if there is open enrollments (active, paused) of that product exist
• [ ] Deny removal if there is open quotations (requested or proposed) of that product
• [ ] Deny removal if product is part of a bundle
• [ ] Deny removal if product is an assigned variant to a proxy
• [ ] Remove Bookmarks of that Product
• [ ] Remove Cart Positions of that Product
• [ ] Throw nice and clean appropriate error messages for the denial cases