PistonArmBlockEntity
Latest successfully changed state progress, which determine piston movement.
Required by redstone state, if nothing blocking way, piston moves.
Percent between 0 and 1 (with in-game step 0.5), where 1 means activated.
Currently state, 0 means pulled, 1 moving and 2 pushed.
Whether piston crafted with slime and can transfer blocks back.
Block Entity will be saved without instantiating new one when transporting (via pistons, commands, etc.).