Billboard Engine

First release.

• Selector Wand marks a flat wall up to 256 x 64; the Billboard Engine behind it scrolls a 5x7 text across it.
• Any full block can be the pixel; it is not used up. Speed 1 to 10, Go / Stop / Restore.
• The original wall is backed up in the world save and comes back on Restore or when the engine is broken.
• While shown, the wall is protected against players, explosions, pistons, mobs and /setblock.
• Redstone friendly: redstone blocks as pixels drive lamps, dust, repeaters and comparators behind the wall like a punch card; levers and torches on the wall stay attached.
• Sign on the engine plus a redstone pulse shows the sign's text; a running engine follows edits to the sign (also from Create's Display Link).
• Optional CC: Tweaked support: the engine is a billboard_engine peripheral.