Bug 1030972 - Import tasks from Bugzilla

@bobsilverberg @Osmose r?
@Osmose Maja and I have been discussing this approach to `ImportTasksView` and I was hoping you might be able to take a peek and let us know what you think. At first glance it seems overly complex and clunky to me, but that might just be my lack of experience with django and trying to push its envelope. Is this code an approach that you might take to the problem? Does another, simpler, approach come to mind for you, and if so, could you give us some guidance towards that? My initial suggestion was to break it up into separate views, but Maja is concerned that that will only introduce new problems that she has already solved with this approach.