ControlledVocab should report prettier errors for failed deletes

Splitting the following scenario from STCOM-228 into a separate feature.

1. Scenario CB: Adding this scenario mid-sprint per discussion with the tech team on roundup. Disabling the delete button, while better from a UX perspective, isn't technically feasible.
   • Given a controlled vocab value is in use by one or more record
   • When delete button is clicked
   • Then:
     • No deletion will occur and popup will appear
     • Popup should display:
       • Header: Cannot delete <controlledVocabType>
       • Body: This <controlledVocabType> cannot be deleted, as it is in use by one or more record.
       • Buttons: Okay

Currently, an alert() is shown by the Redux middleware epic. We want to be able to catch those 400 errors and display them better, though.