Doc: Edit info about state chart editor

- Convert paragraphs and lists into tables with icons to allow
  users to browse easier
- Move the info about using the wizard into a how-to topic
- Add subtitles
- Move the topic to Reference

Task-number: QTCREATORBUG-29361
Fixes: QTCREATORBUG-29766
Change-Id: Id9c1aabd8f3a7bfb0659898dd329cedbcbb5f697
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

doc/qtcreator/src/qtcreator.qdoc

@@ -67,7 +67,6 @@
                     \li \l{Refactoring}
                     \li \l{Configuring the Editor}
                     \li \l{Modeling}
-                    \li \l{Editing State Charts}
                 \endlist
         \row
             \li \inlineimage front-preview.png