Allow targeting players; Make other players hostile (until there are factions and PVP flags in place)
Separate other Player's from the actual player on the client; Allow Free-for-all PVP; Turn cursor into a sword when hovering players

* Add a Hero class, separating other Player's from the actual player on the client.
* Support damaging another player. In the future, there will be factions and PVP flags to determine if it's possible to attack another player.