mvm_boreal a2a

Update Alpha 2a
Changes:
- Put the navmesh file into the .zip because I'm not sure if that's important for an MVM map but I don't want to risk it

Alpha 2 Update Changes:
- Added some small ammo packs near the end of the wooden bridge
- Adjusted lighting so the HDR is less intensive and some areas are les dark
- Actually made the cubemaps work
- Added a Mann Co. sign to the front of the base
- Properly repacked the map, greatly reducing the bsp file size