Fixed the half-done hunger implementation, fixed lots of bugs related to hunger

- Fixed starvation doesn't deal any damage at all (Human->getFood() returns a float, not an int, === 0 won't work so great)
- Added exhaustion for sprinting, walking, jumping and sprint-jumping as per MCPE (these use MCPE values, and yes MCPE does walking exhaustion!)
- Fixed attributes don't get reset after player death
- Added food and hunger regeneration in peaceful difficulty
- Added API methods Living->jump() (motion isn't updated yet, so this won't actually do much if plugins try to use it) and Living->getJumpVelocity()

TODO: implement exhaustion for swimming

src/pocketmine/event/player/PlayerExhaustEvent.php

@@ -34,19 +34,21 @@ class PlayerExhaustEvent extends PlayerEvent implements Cancellable{
 	const CAUSE_HEALTH_REGEN = 4;
 	const CAUSE_POTION = 5;
 	const CAUSE_WALKING = 6;
-	const CAUSE_SNEAKING = 7;
+	const CAUSE_SPRINTING = 7;
 	const CAUSE_SWIMMING = 8;
-	const CAUSE_JUMPING = 10;
+	const CAUSE_JUMPING = 9;
+	const CAUSE_SPRINT_JUMPING = 10;
 	const CAUSE_CUSTOM = 11;
 
-	const CAUSE_FLAG_SPRINT = 0x10000;
-
 	/** @var float */
 	private $amount;
+	/** @var int */
+	private $cause;
 
 	public function __construct(Human $human, float $amount, int $cause){
 		$this->player = $human;
 		$this->amount = $amount;
+		$this->cause = $cause;
 	}
 
 	/**
@@ -63,4 +65,12 @@ class PlayerExhaustEvent extends PlayerEvent implements Cancellable{
 	public function setAmount(float $amount){
 		$this->amount = $amount;
 	}
+
+	/**
+	 * Returns an int cause of the exhaustion - one of the constants at the top of this class.
+	 * @return int
+	 */
+	public function getCause() : int{
+		return $this->cause;
+	}
 }