Binary strict types (#969)

* Some Binary cleanup, type-hints and strict types
yes, I know this is very crashy... that's good, because it highlights unexpected behaviour

* added some default values

src/pocketmine/network/mcpe/protocol/DataPacket.php

@@ -19,6 +19,8 @@
  *
 */
 
+declare(strict_types=1);
+
 namespace pocketmine\network\mcpe\protocol;
 
 #include <rules/DataPacket.h>