Expressions: Fix property editor behavior

- change responsibility of python code emition
- Correct python code handling for expressions
- handle constraints expressions handling

src/Mod/Sketcher/Gui/PropertyConstraintListItem.cpp

@@ -103,7 +103,7 @@ void PropertyConstraintListItem::initialize()
             }
             
             item->bind(list->createPath(id-1));
-            item->setAutoApply(true);
+            item->setAutoApply(false);
         }
     }