[COMMANDS] Add vcpu monitor command

This patch adds monitor sub-command to vcpu command. The new
command periodically prints CPU, RAM, VAPOOL, and VCPU status
just like linux top command. It uses VT100 console commands
to refresh screen and reset cursor position periodically. The
commands works fine with serial port, telnet connection, and
framebuffer character device.

This patch is inspired from patch "[DAEMONS] Add a monitor
daemon, with compatibility with framebuffers." submitted
by Jimmy.

Signed-off-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Jimmy Durand Wesolowski <jimmy.durand-wesolowski@openwide.fr>
[COMMANDS] The RGB565 built-in logo can now be selected in the menu.

There are actually two logos availables, Xvisor's or the SystemX Technological
Research Institute.
Both are in RGB565 format for the moment.

Signed-off-by: Jimmy Durand Wesolowski <jimmy.durand-wesolowski@openwide.fr>
[COMMANDS] Correcting the fb image command dependency.

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