Doc: Add links to the index page

Create links for the topics mentioned on the index page for
Qt Framework, Qt Creator, Tools and Toolchains, and Licenses
Used in Qt.

Task-number: QTBUG-42552
Change-Id: Ia493e88fcb93319cacd5997288ab0f3b832d064c
Reviewed-by: Tuukka Turunen <tuukka.turunen@digia.com>
Reviewed-by: Venugopal Shivashankar <venugopal.shivashankar@digia.com>

doc/src/index.qdoc

@@ -42,29 +42,32 @@
                 \div {class="icons1of3"}
                     \image landing/icon_Qt_78x78px.png
                     \section1 Qt Framework
-                    Intuitive APIs for C++ and JavaScript-like
-                    programming with Qt Quick for rapid UI creation.
+                    Intuitive \l{Qt Reference Pages}{API}s for \l {All Classes}{C++}
+                    and JavaScript-like programming with \l{QML Applications}{Qt Quick}
+                    for rapid UI creation.
                 \enddiv
                 \div {class="icons1of3"}
                     \image landing/icon_QtCreator_78x78px.png
                     \section1 Qt Creator IDE
-                    A powerful cross-platform integrated development
-                    environment, including UI designer tools and on-device
-                    debugging.
+                    A powerful cross-platform \l{Qt Creator Manual}
+                    {integrated development environment}, including
+                    \l{Qt Creator: Designing User Interfaces}{UI designer}
+                    tools and on-device \l{Qt Creator: Debugging}{debugging}.
                 \enddiv
                 \div {class="icons1of3"}
                     \image landing/icon_Tools.png
                     \section1 Tools and Toolchains
-                    Internationalization support, embedded toolchains, and more.
+                    \l{Internationalization with Qt}{Internationalization} support,
+                    \l{Qt for Embedded Linux}{embedded} toolchains, and more.
                 \enddiv
                 \enddiv
                 \section1 Licenses Used in Qt
 
                 Qt Framework and tools are available under both open-source and
-                commercial licenses.
+                commercial \l{Qt Licensing}{licenses}.
 
                 The commercially licensed Qt contains additional functionality and
-                productivity tools. For details, see \l{http://www.qt.io/}.
+                productivity tools. For details, see \l{http://www.qt.io/download/}.
     \enddiv
     \div {class="col-2 sidebar"}
             \div {class="sectionlist normallist"}