Tell the user why issues in a view cannot be reordered when the Sort order is not set to Rank

If a user attempts to reorder issues in an Advanced Roadmap plan but the sort order for the view is set to something other than Rank, the reordering has no effect. However, the user does not know why they can't reorder the issues. If fact, it appears that they can (they can drag and drop issues), but the changes do not stick. It would be nice to display a message to the user explaining that they cannot reorder issues unless the view is sorted by Rank.