DirectShow: Refactor camera backend.

Almost entire rewrite of the camera backend. It doesn't provide new
features but is more stable and behave as it should.

- Correctly report camera state and status
- Correctly report if the camera is ready to capture
- Emit imageExposed() signal
- Save captured images in an appropriate directory
- Images can be captured even without a viewport
- Better error handling

Removed the custom QVideoWidgetControl as it doesn't provide anything more
than the QVideoWidget's renderer control fallback.

Task-number: QTBUG-33782
Change-Id: I9baf6f83e7c69619f20a101921f7865a1c90d5e4
Reviewed-by: Christian Stromme <christian.stromme@digia.com>

src/plugins/directshow/camera/dscameraservice.h

@@ -70,13 +70,9 @@ private:
     DSCameraControl        *m_control;
     DSCameraSession        *m_session;
     DSVideoOutputControl   *m_videoOutput;
-#if defined(HAVE_WIDGETS)
-    QMediaControl          *m_viewFinderWidget;
-#endif
     DSVideoDeviceControl   *m_videoDevice;
     QMediaControl          *m_videoRenderer;
     DSImageCaptureControl  *m_imageCapture;
-    QByteArray m_device;
 };
 
 QT_END_NAMESPACE