[FEATURE]: Warning and option to change .obj coordinate frame

**Is your feature request related to a problem? Please describe.**
Blender loads .obj files with a default rotation along the x-axis of 90 degree. This is in line how many datasets such as ShapeNet and SunCG define the orientation of their 3D models. However for object pose estimation it is quite unintuitive to transform the original vertex coordinates at load time.

**Describe the solution you'd like**
A warning about the coordinate system change `(x,y,z) -> (x,-z, y)`. An option to change the target coordinate system at load time to something else.

**Describe alternatives you've considered**
Loading the object vertices without transformations. But this deviates from the default blender behavior.