Multipalette de-briefing

I do want to have multi-palette in AnimEDS as well, so that you can tint your monsters and reuse e.g. the same sprite for Bilou's front and rear foot, or for Bilou and Pendats feet and hands. Right now, each foot sprite is cloned 4 times and I only have 1 monster so far ... seriously.

Allons-y: multi-palettes aussi dans l'éditeur d'animation. C'est vrai, quoi: pouvoir repeindre les bouquins dans l'éditeur de niveau, c'est bien beau, mais ça ne change en rien le fait que je suis obligé de maintenir chaque sprite de pied en 3 coloris séparés et 4 coloris pour les pieds. Vous comprenez bien que dans un contexte pareil, tenter de faire un "pendat" avec les pieds et les mains blanches (couleur règlementaire dans l'armée de Sqrt) est totalement hors de question >_<.

So it's time I track the core changes made to Level Editor so that it can benefit from multi-palettes:

• Initialisation of the Engine object needs an  (EXTENDED_PALETTES) additional argument;
• every call that sets DISPLAY_BGx_ACTIVE now also need to set DISPLAY_BG_EXT_PALETTE;
• SpriteRam should no longer be initialised with e.g. SPRITE_PALETTE but with one of the slots returned by Engine::editpal($slot,false));
• when calling SpriteSet::setpalette() to copy from/to VRAM, make sure you call  Engine::editpal($slot,true); before copying and Engine::editpal($any,false); when you're done.
• before loading a SPR file, define SpriteSet::ncolors and wrap SpriteSet::Load() with Engine::editpal calls as needed.

Now, AnimEDS will mostly require extended palettes for sprites, not for simply for tiles. So ...

• [done] make AnimEDS compile in the noswap branch
• [done] get rid of logo display.
• [done] only MAIN screen is given multi-pal capabilities. Tell GuiEngine on which screen console should be ; Window provide palette[] and layers abstract registers ?
• [done] move AnimWindow on MAIN screen; fix sprite-based widgets.
• [done] make sure a palette is initialised