Usability changes to Contrib Key Sorting Feature

@kcarcia, this addresses the issues we discussed today.  The drop down menu now has the same letter as the letter chosen to overlay the key, the first label (A) is assigned to the contributor key that was first used to upload a data set in order to preserve ordering/not reorder everything if a new key is added.  Did a final round of usability testing and everything (thankfully) looked as though it was behaving in the way we intended.