Allow instance administrator to edit any issue.
Allow instance administrator to edit any issue.

They have access to the database so they could modifying it by hand but
modifying from the UI makes more sense.

Author: ted.mielczarek@gmail.com

Review: https://codereview.appspot.com/7237072/

riannucci/rietveldv2,riannucci/rietveldv2