Removed entanglement between chunks and providers. WARNING: BREAKING API CHANGES.

- All entity and tile constructors now require a \pocketmine\level\Level instead of a \pocketmine\level\format\Chunk.
- Chunk->getProvider() and Chunk->setProvider() have been removed.
- Chunk::__construct() has had the $provider parameter removed.
- Chunk->unload() has had the unused $save parameter removed.
- ChunkEvents now take a Level parameter instead of going through the Chunk

API bump to 3.0.0-ALPHA4

src/pocketmine/level/generator/GenerationTask.php

@@ -75,7 +75,7 @@ class GenerationTask extends AsyncTask{
 				return;
 			}
 			/** @var Chunk $chunk */
-			$chunk = Chunk::fastDeserialize($this->chunk, $level->getProvider());
+			$chunk = Chunk::fastDeserialize($this->chunk);
 			if($chunk === null){
 				//TODO error
 				return;