Fix up a few doc issues

* lingering references to Mobility
* missing group tags on some classes meant they went missing
* put classes into functional groups as well (e.g. audio, camera)
* added some of the qdoc files to OTHER_FILES so they show up in Creator

There are still a lot of warnings since it seems like qdoc is not
processing the controls directory.

Change-Id: I036f8826ae63f8273b3e649cb32c091d964ce830
Reviewed-by: Jonas Rabbe <jonas.rabbe@nokia.com>

src/multimedia/video/qabstractvideobuffer.cpp

@@ -65,6 +65,8 @@ namespace
     \class QAbstractVideoBuffer
     \brief The QAbstractVideoBuffer class is an abstraction for video data.
     \inmodule QtMultimedia
+    \ingroup multimedia
+    \ingroup multimedia_video
 
     The QVideoFrame class makes use of a QAbstractVideoBuffer internally to reference a buffer of
     video data.  Quite often video data buffers may reside in video memory rather than system

src/multimedia/video/qabstractvideosurface.cpp

@@ -83,6 +83,9 @@ public:
     \brief The QAbstractVideoSurface class is a base class for video presentation surfaces.
     \inmodule QtMultimedia
 
+    \ingroup multimedia
+    \ingroup multimedia_video
+
     The QAbstractVideoSurface class defines the standard interface that video producers use to
     inter-operate with video presentation surfaces.  You can subclass this interface to receive
     video frames from sources like \l {QMediaPlayer}{decoded media} or \l {QCamera}{cameras} to

src/multimedia/video/qvideoframe.cpp

@@ -126,6 +126,9 @@ private:
     \brief The QVideoFrame class represents a frame of video data.
     \inmodule QtMultimedia
 
+    \ingroup multimedia
+    \ingroup multimedia_video
+
     A QVideoFrame encapsulates the pixel data of a video frame, and information about the frame.
 
     Video frames can come from several places - decoded \l {QMediaPlayer}{media}, a

src/multimedia/video/qvideosurfaceformat.cpp

@@ -153,6 +153,9 @@ public:
     surface.
     \inmodule QtMultimedia
 
+    \ingroup multimedia
+    \ingroup multimedia_video
+
     A video surface presents a stream of video frames.  The surface's format describes the type of
     the frames and determines how they should be presented.