The multi-lang flow doesn't let you add a job label

Problem/Motivation

It's way easier to keep track of your jobs if you can add a custom label. Right now if you use the "Request multiple translations" button, there's no way to add a job label.

Steps to reproduce

- add something to your cart
- submit it for translation using "Request multiple translations"
- observe that you never had a chance to add a label

Proposed resolution

Add a label textfield to the multi_lang box, and save the label along with the job.