changelog a2 -> b1:
Gameplay:
- Made oasis walljump over old city wall impossible
- Tunnels are now connected so both wells can be used to access Old City to blow the wall or grab the flag
- Added a door in tunnels near exit to guns that only opens when old city wall has been blown (like ET sw_oasis_b3)
- flag is removed once old city wall has been destroyed (if captured by allies)
- Added upper garrison spawn for axis (default spawn, max 2 players will spawn here)
- Changed timelimit from 15 -> 12
- Added axis teamdoors back

Map Layout:
- Made the corridor wider near old allied command post (upper passage from allies spawn)
- Removed rubble (rock + wood) in passage next to broken roof
- Removed rocks near flag spawn stairs 
- Removed clipping at most stairs to prevent bumping effect (like on adlernest_b3)

Other:
- Added target locations (teamoverlay locations)
- Added sounds 
- Gun models go in destructive state once blown with dynamite
- Added burning tank back after fence behind the guns 
- Fix conflicting shader with te_delivery_b1 (seawall_wall/metal_trim1 on generators outside axis north gun)
- Fix texture glitch (near entrance tunnel flag)
- Removed a vase after old city wall that was texture buggy
- Added levelshots

TODO:
- end game: fire north/south guns (axis win) + sounds 
- end game: entrance tank on courtyard (allies win) + sounds 
- north/south gun explosions sounds + smoke 
