[COMMANDS] Adding the "fb image" command, to display an image on a framebuffer.

This "fb image" command takes the following argument:
- the framebuffer to display the image on
- the image path
- the "x", the horizontal offset on the screen
- the "y", the vertical offset on the screen

Signed-off-by: Jimmy Durand Wesolowski <jimmy.durand-wesolowski@openwide.fr>