Apply scale of collision meshes when exporting

[Amudtogal]

Is your feature request related to a problem? Please describe. As URDF and other export formats can not deal with scaled collision meshes, we need to apply any remaining scales before exporting (and thus, create new mesh objects as required).

Describe the solution you'd like We should run this prior to export as part of our tests. Maybe we could even gather all the meshes that relate to the same scale and visual and export them only once.

Describe alternatives you've considered

Additional context See #173 for the current quickfix.