Integrate intro screens

[shazz]

• add boot logo (Calvin)
• add intro screen (CODEF based)

[melonjs]

I just realized I used the intro screen as a demo for the CODEF integration (while entering a door). we need to discuss anyway on how to do this, there is a couple of possibility :

• make the boot logo the actual loader, and then switch from screen to screen until we reach the menu
• manually preload each time what we need for the boot logo and the intro screen (as I've done for the current loader), and then in the main, instead of directly switching to the loader, first swith to the intro, and once the intro is finished, switch to the loader from the intro screen.