trimesh->tri
clean up of some namespaces to comply the following naming:
Complexes (3 letters namespaces):
order 0 (point cloud ) :vrt
order 1 (edge meshes) :edg
order 2 (triangle meshes) :tri
order 3 (triangle meshes) :tet
Simplexes (4 letters namespaces):
order 0 (vertex) :vert
order 1 (edge) :edge
order 2 (triangle) :triangle
order 3 (tetrahedron) :tetrahedron
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