Improvements to Zombies

Bug Fixes

1.) Zombies no longer walk through objects. That's right, no more phasing through matter! 

     -Made the objects in the scene into Static Navmesh objects so that zombies can't walk through them.

2.) Once Zombies are (fully) dead they no longer get in your way. No more blocking the doorway.

     - Capsule collider is removed from zombies when they die. 

Bugs still aware of:

1.) Zombies won't cross the threshold of doors. (They must be confusing themselves with vampires). 

     - There is a spot missing in the navmesh for this and I'm not sure why.