Update documentation.

Rewrite the module overview, add video and audio overviews,
and update the camera overview. Tweak the radiooverview
slightly.

Still missing some links for examples and some fleshing out
but hopefully a lot better.

Change-Id: Id6486e20ba4a09c36d7739e327d4f9910ad083a5
Reviewed-by: Jonas Rabbe <jonas.rabbe@nokia.com>

doc/src/snippets/multimedia-snippets/video.cpp

@@ -47,6 +47,7 @@
 #include "qvideowidgetcontrol.h"
 #include "qvideowindowcontrol.h"
 #include "qgraphicsvideoitem.h"
+#include "qmediaplaylist.h"
 
 #include <QFormLayout>
 #include <QGraphicsView>
@@ -63,6 +64,7 @@ public:
 private:
     // Common naming
     QMediaService *mediaService;
+    QMediaPlaylist *playlist;
     QVideoWidget *videoWidget;
     QWidget *widget;
     QFormLayout *layout;
@@ -85,12 +87,15 @@ void VideoExample::VideoWidget()
     //! [Video widget]
     player = new QMediaPlayer;
 
-    videoWidget = new QVideoWidget;
+    playlist = new QMediaPlaylist(player);
+    playlist->addMedia(QUrl("http://example.com/myclip1.mp4"));
+    playlist->addMedia(QUrl("http://example.com/myclip2.mp4"));
 
+    videoWidget = new QVideoWidget;
     player->setVideoOutput(videoWidget);
-    player->setMedia(QUrl("http://example.com/movie.mp4"));
 
     videoWidget->show();
+    playlist->setCurrentIndex(1);
     player->play();
     //! [Video widget]
 }
@@ -123,7 +128,7 @@ void VideoExample::VideoGraphicsItem()
     graphicsView->scene()->addItem(item);
     graphicsView->show();
 
-    player->setMedia(video);
+    player->setMedia(QUrl("http://example.com/myclip4.ogv"));
     player->play();
     //! [Video graphics item]
 }