* Event handlers always handle subclass events. public static $handlerList no longer required.
* Removed $handlerList declarations
* HandlerList cleanup: Removed HandlerList->handlers and related bake methods
* Removed obsolete Event->getHandlers()
* EventPriority: Added fromString()
* PluginManager: throw exceptions on registering handlers with invalid priorities
This allows specifying a handler of `EntityDamageEvent` which will handle any instanceof it (as per current behaviour), AND also now allows specifying a handler specifically for `EntityDamageByEntityEvent`, which only handles `EntityDamageEvent`.
This was not previously possible due to limitations in the way handlers were registered.
Abstract events may not be handled unless they declare the `@allowHandle` PhpDoc tag.
- 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
