Show graded icons in more places

In the course outline, if a subsection has any graded content,
show a graded icon (the pencil icon).

Also, show the graded icon for LTI xmodule units (xblocks is a
different repo, but will get same treatment).

AA-75

common/lib/xmodule/xmodule/lti_module.py

@@ -345,7 +345,8 @@ class LTIModule(LTIFields, LTI20ModuleMixin, XModule):
         ]
     }
     css = {'scss': [resource_string(__name__, 'css/lti/lti.scss')]}
-    js_module_name = "LTI"
+    js_module_name = 'LTI'
+    icon_class = 'problem'
 
     def get_input_fields(self):
         # LTI provides a list of default parameters that might be passed as