MDL-9506 Removed the debugging message for the fetch() methods. Added droplow and keephigh rules to grade_category::aggregate_grades(). The only question now is what to do when the droplow or keephigh field is larger than the number of grades for a given user/item combination. At the moment it just gives that value 0.

lib/grade/grade_outcome.php

@@ -117,7 +117,6 @@ class grade_outcome extends grade_object {
                 return $grade_outcome;
             }
         } else {
-            debugging("No matching grade_outcome in DB with the given criteria.");
             return false;
         }
     }