NavMesh generates 90 degrees rotated for custom collisions

The NavMesh creates breaks at the wrong rotation if the mesh is using collision created from outside of UE4.

This is obvious in a lot of the market content with special collision created in maya/3dsmax

1. Create a top-down template project
2. Download and extract the attached file
3. Place the AncientRuins folder in the Content folder of the project
4. Place the Ruins_14 asset in the level
5. Show navigation