Nuke Block->meta, split into variant and state properties, lots of cleanup

This is a major change to the way block metadata is handled within the PM core. This separates variant metadata (which really ought to be part of the ID) from state metadata, and in a couple of cases flattens separate states of blocks together.

The result of this is that invalid variants can be much more easily detected, and additionally state handling is much cleaner since meta is only needed at the serialize layer instead of throughout the code.

src/pocketmine/block/FlowerPot.php

@@ -33,14 +33,26 @@ use pocketmine\tile\Tile;
 
 class FlowerPot extends Flowable{
 
-	public const STATE_EMPTY = 0;
-	public const STATE_FULL = 1;
-
 	protected $id = self::FLOWER_POT_BLOCK;
 	protected $itemId = Item::FLOWER_POT;
 
-	public function __construct(int $meta = 0){
-		$this->setDamage($meta);
+	/** @var bool */
+	protected $occupied = false;
+
+	public function __construct(){
+
+	}
+
+	protected function writeStateToMeta() : int{
+		return $this->occupied ? 1 : 0;
+	}
+
+	public function readStateFromMeta(int $meta) : void{
+		$this->occupied = $meta !== 0;
+	}
+
+	public function getStateBitmask() : int{
+		return 0b1111; //vanilla uses various values, we only care about 1 and 0 for PE
 	}
 
 	public function getName() : string{
@@ -80,17 +92,13 @@ class FlowerPot extends Flowable{
 			return true;
 		}
 
-		$this->setDamage(self::STATE_FULL); //specific damage value is unnecessary, it just needs to be non-zero to show an item.
+		$this->occupied = true;
 		$this->getLevel()->setBlock($this, $this, true, false);
 		$pot->setItem($item->pop());
 
 		return true;
 	}
 
-	public function getVariantBitmask() : int{
-		return 0;
-	}
-
 	public function getDropsForCompatibleTool(Item $item) : array{
 		$items = parent::getDropsForCompatibleTool($item);