rename: Ease up setting a different index

To set index "2" you only have to enter "2" and not "#2" (which wasn't
indicated anywhere in the tool).

src/python/klausurarchiv/renaming.py

@@ -608,8 +608,8 @@ class RenameActivity:
           s.date=s.query
           s.clear_query()
           return True
-        elif re.fullmatch("#[1-9][0-9]*",s.query):
-          s.index=int(s.query[1:])
+        elif re.fullmatch("[1-9][0-9]*",s.query):
+          s.index=int(s.query)
           s.clear_query()
           return True
         elif len(s.query)>0: