Ensure every ajax request throws an error that end users can understand

Added new error messages to:
 1) assets/javascripts
    a) data_sets/
    b) news
    c) projects/
    d) shared/media_objects_view
    e) tutorials/show
    f) users/show
 2) lib/assets/javascripts
   a) content_edit_pane
   b) highvis/savedVis
   c) info_edit
   d) name_popup