Attack system on rabbits, no item drops yet

@PimV, @sagar193, @jhay 

needed to work around an crash, for some reason the killed rabbit isn't properly removed for the list.
That's why the respawn looks so odd.
Waarom een "Attackable" enum hier? Is niet echt zo van: "Ik attackable" (maar wel: "Ik attack met Spear" of "Ik chop")?