Can walk up "stair-steps". Cleanup WIP.

Better performance in RectanglevsTriangle check.
Added IsOnGround flag and VerticalStepHeight in Physics.
Lotsa commented code saved for historical reasons, remove later.

include/Engine/Collision/Collision.h

@@ -68,6 +68,8 @@ bool AABBvsTriangles(const AABB& box,
     const std::vector<unsigned int>& modelIndices,
     const glm::mat4& modelMatrix,
     glm::vec3& boxVelocity,
+    float verticalStepHeight,
+    bool& isOnGround,
     glm::vec3& outResolutionVector);
 
 //Return true if the boxes are intersecting.