Make default error strings use "result/oracle" jargon

sznqalibs/hoover.py

                 diff = jsDiff(dira=case['oracle'],
                               dirb=case['result'],
                               namea=case['oname'],
-                              nameb=case['rname'])
+                              nameb=case['rname'],
+                              chara='o',
+                              charb='r')
 
             tracker.update(diff, argset)