Bug 1030972 - Import tasks from Bugzilla

@bobsilverberg @Osmose r?
@mjzffr We discussed this issue yesterday and it was decided that we do not want to change the flow to add the invalidation criteria at the end. If it will help to break the import into more steps, where first the Task Form is processed, and then a separate screen for invalidation criteria is presented, and *then* the confirmation screen is shown, then that would be fine. If that's not going to help the situation then let's just forget about it for now.

In any case, the tasks to focus on for today and tomorrow are, in this order:
1. Address review comments (except for refactoring this view).
2. Add unit tests.
3. Address the issues with this view, if practical.