Misc. typo and whitespace fixes

ref: https://forum.freecadweb.org/viewtopic.php?f=3&t=30988#p256964
along with other misc. fixes

src/Gui/CommandDoc.cpp

@@ -1120,8 +1120,8 @@ void StdCmdDelete::activated(int iMsg)
                         }
                     }
                 }
-                
-                //check for inactive objects in selection  Mantis #3477
+
+                //check for inactive objects in selection (Mantis #3477)
                 std::set<QString> inactiveLabels;
                 App::Application& app = App::GetApplication();
                 App::Document* actDoc = app.getActiveDocument();