Relation unit errors

This branch adds the units in error to the relation tab in the inspector. There are only unit tests because the timings are unreliable for a purely js test and would require a settimeout/polling. It would be better tested using selenium.

To QA:
deploy mysql & wordpress
relate them
scale one to 100 units with the simulator on and then switch to the relations tab
once there is a unit in relation error it will show up in the list.
scale it down to 1 unit and switch back to the relations tab quickly you should notice it dissappear.