image : to display an image component (only one component of type image can be rendered)
note that the texture is never cleared, nor reloaded (in case of configuration modification).
image_max_width: by default, the width of the image is the one of the pannel (value is 0). with this
option, you can reduce it.
image_background: global background image to display
Signed-off-by: Nicolas Adenis-Lamarre <nicolas.adenis.lamarre@gmail.com>