Doc: move imageviewer docs from headers to cpp files

Use standard wording for function docs. Use valid
QDoc commands (\a instead of \param, for example).

Change-Id: I556fdbf686f2f54138617d6784c650a1d973513c
Reviewed-by: Eike Ziller <eike.ziller@digia.com>

src/plugins/imageviewer/imageviewer.h

@@ -79,12 +79,7 @@ private slots:
     void playToggled();
 
 private:
-    /*!
-      \brief Try to change button's icon to the one from the current theme.
-      \param button Button where an icon should be changed
-      \param name Icon name in the in the current icon theme
-      \return true if icon is updated, false otherwise
-     */
+
     bool updateButtonIconByTheme(QAbstractButton *button, const QString &name);
     void setPaused(bool paused);