Fix external links to Qt Creator Manual

The section name changed in the Qt Creator Manual and
external-resources file.

Change-Id: I6f547b161bdb17eab6cfec2e636be050540ba428
Reviewed-by: Venugopal Shivashankar <Venugopal.Shivashankar@qt.io>
Reviewed-by: Paul Wicking <paul.wicking@qt.io>

doc/src/qmlapp/applicationdevelopers.qdoc

@@ -75,7 +75,7 @@ provided by Qt Quick, please see the \l{Qt Quick} module documentation.
 
 For creating or customizing graphical user interfaces, Qt Quick adds visual
 types, animation types, and other QML types in addition to the standard QML
-types from Qt QML. \l{Qt Creator: Using Qt Quick Designer}{Qt Quick Designer}
+types from Qt QML. \l{Qt Creator: Editing QLM Files in Design Mode}{Qt Quick Designer}
 is integrated within Qt Creator and supports \c{QtQuick 2} from Qt Creator
 version 2.7 and onwards.
 

doc/src/qt5-intro.qdoc

@@ -234,7 +234,7 @@
     Qt Quick Controls and Qt Quick Layouts provide a vast set of UI controls
     ranging from the most basic text field and button to the more complex
     stack view and tumbler. The controls are also made available in
-    \l{Qt Creator: Using Qt Quick Designer}{Qt Quick Designer}.
+    \l{Qt Creator: Editing QLM Files in Design Mode}{Qt Quick Designer}.
     \raw HTML
       </td></tr>
      </table>

doc/src/whatsnew/whatsnew51.qdoc

@@ -185,7 +185,8 @@
 
     \list
     \li Improved C++11 code editing support
-    \li \l{Qt Creator: Using Qt Quick Designer}{Qt Quick Designer} with full support for Qt Quick
+    \li \l{Qt Creator: Editing QLM Files in Design Mode}{Qt Quick Designer}
+        with full support for Qt Quick
     \li Android \l{Qt Creator: Deploying Applications to Android Devices}{development target}
     \li Experimental QBS and diff integration
     \endlist