Return associations on remove association

[wbhob]

Issue Description

When removing an association (DELETE /product/:product/association/:association) it should also return the updated array of associations on the product (currently returns the product instance)

Environment

• node version: ???
• fabrix version: ???
• operating system: ???

[scott-wyatt]

It should technically return the association that was removed. That's part of some methodology that I can't remember the name of right now. But's basically like "Confirm that thing that was deleted so you can undo it"