Add general metadata for camera frames/captures

Add support for delivering general metadata of the camera frames and of captured images to applications. These are important details that application might need to make use of camera functionality - both on-going or at the moment of image capture.
Both encoded formats (jpeg) and unencoded formats (DNG raw, YUV formats) should be allowed to be returned.
For image capture, while the encoded formats allow for capture parameters to be retrived as EXIF fields, support should be added to retrieve these parameters for unencoded formats.
There have been already good discussion on the topic, and agreement about the needs during the Qt Multimedia Workshop. This was agreed it is a top priority issue for the 1.3 QtMultimediaKit. This requirement also includes returning of the face coordinates from the camera face tracker system.