1752850: Job splitting

As jobs hit the system they tend to be described at a very high level. This is exactly what we want as it gives a good basis for refining them. This high level overview rarely gets broken down in a way that means we can track individual jobs and deliverables. This means that things are hard to estimate, the tracking becomes clumsy with the overall effect being that we're not getting as much out of the job tracking as we should be.

One thing that will help us is to be able to split a job down into sub-parts, which can themselves be split again.

We're going to start by creating a simple feature to do this and play around with some ideas for presentation of the jobs and how the statuses of the sub-jobs should affect the status of their parents.

This is installed now. At the moment only site admins have permission to split jobs down.

Once we've confirmed that the procedures work we'll probably permission it in such a way that all project members can split jobs.