[feature]Add source attribute for ActorDeathEvent and is_player attribute for Actor

[umarurize]

Add source attribute for ActorDeathEvent to get source actor (player or entity) who kills the actor involves in ActorDeathEvent

Add is_player attribute for Actor to judge if actor is player or not…..

[xXLarryTFVWXx]

I believe that Player is a child class, so you can check for that by using isinstance(<object>, Player) where <object>is the target or event sender.