Sector Workflow admin.js needs to be removed

Have rebased this across a few branches so ignore all the "added commits" (rewriting history across three different streams).

Not closing this yet until I have a chat with gareth.poole on if we need a 12.0.x merge for this too or if we're going to have a more general rebase on that in the future.

Merged into all active branches

Automatically closed - issue fixed for 2 weeks with no activity.