OmfgZombieslol Patch 1

This patch fixes barricade issues, adds an objective to omfg_overwatch, adds a new map omfg_desertfort, removes crowbar, and tweaks other things.
OmfgZombieslol is my first and last attempt most likely at source zombie mods, L4D will kill this breed >:O In OZL players band together to fight off zombies with a large array of new abilities.