Update setResourcePack for 1.8

In 1.8, the server now specifies a hash when sending a resource pack request to the client.
In addition, it's now possible to determine whether the client accepted or rejected the request, through a new packet type.

This PR allows `Player#setResourcePack` to be called with a hash, and adds `PlayerResourcePackStatusEvent` to allow plugins to determine the result.
@turt2live: I'm not adding it, it already exists. The diff is just showing it in a weird way. I'm keeping it for backwards compatibility.