Outbreak a3

-Extended the roof gameplay for zombies, made the roofs higher.
-remade the sewers
-brought back the second roof for survivors, but made it a bit more harder to defend.
-added another zombie exit and remade the roof alley area near the big roof, updated the big roof.
-added more roof accessibility for zombies near the big roof.
-added more minor detailing.

-Removed the stair to the small roof near red spawn
-Removed the roof spawn for zombies near gas station
-Moved the zombie spawns back from the gas station area

-Added sewer
-Moved the zombie exits near the red spawn to prevent spam
-Added a roof spawn for zombies near red spawn
-Added another route from the second floor building near red spawn
-Added another roof zombie spawn on top of the new route
-Improved clipping near gas station
-Added a new route for the zombie spawn near the second roof spot
-Added a new stair to the second roof spot

-New skybox
-Added new signs