Engineer Bug by Census Unassigning

Using the Unassign button in the Census on an engineer tends to move it into the broken state of all them all displaying as free while being unable to be put to work. Fixed by removing all engineers and re-adding them.

At a guess it might be that the census unassign buttons call to unassignJob() doesn't call sim.unassignCraftJobIfEngineer()

While the normal add/remove engineers does via btn.unassignJobs() => sim.removeJob();