[C++][Python][Major] Replaced the way collisions and visuals are stored in...

[C++][Python][Major] Replaced the way collisions and visuals are stored in GeometryModel. Now it is two lists of GeometryObject (one for collisions, one for visuals) aggregating information instead of multiple vectors. Now handle multiple collisions/visuals for one link when parsing urdf file and keep track of the mesh absolute path. Changed binding accordingly.