v4l2object: set colorspace for output devices
v4l2object: set colorspace for output devices

When the v4l2 device is an output device, the application shall set the
colorspace. So map GStreamer colorimetry info to V4L2 colorspace and set
on set_format. In case we have no colorimetry information, we try to
guess it according to pixel format and video size.

https://bugzilla.gnome.org/show_bug.cgi?id=737579

wkatsak/gst-plugins-good,wkatsak/gst-plugins-good,jpakkane/gstreamer-plugins-good,ndufresne/gst-plugins-good,jpakkane/gstreamer-plugins-good,vatavuserban/gst-plugins-good,vatavuserban/gst-plugins-good,ndufresne/gst-plugins-good,vatavuserban/gst-plugins-good,jpakkane/gstreamer-plugins-good,wkatsak/gst-plugins-good,wkatsak/gst-plugins-good,vatavuserban/gst-plugins-good,ndufresne/gst-plugins-good,jpakkane/gstreamer-plugins-good,ndufresne/gst-plugins-good