Removing invisible walls

[CamoRF]

• Would be useful for when making maps using existing terrain and might be the most simple thing to try first with editing terrain data. They go up to y=1000 in SP, will doublecheck MP/WC later.

[CamoRF]

I suspect they're a box collider defined in the havok blocks. I also suspect that the terrain meshes we use so far aren't used for collision and instead there's a version of them in the havok data block for collision. haven't confirmed but it'd make sense to have all your collision data in a format that havok can easily load and use vs having to convert the render mesh at runtime. would also fit the games approach to designing the formats that are ready to use with very little parsing or conversion.