Breakdown story should not move to the bottom of backlog

Given a long backlog breaking down a story is painful because it moves all the new sub-stories to the end of the backlog. Instead, I'd prefer all the sub-stories to be placed in the _same_ location where the parent was.

This avoids having to scroll to the bottom, identify the sub-stories, and then drag them up to the former location of the parent if I can remember where that was. Way too much effort.