Merge branch 'featureOBJReader3dTexcoords' into 'master'

texcoord3d support for obj loader

closes #19 

unfortunately the other supported file formats dont seem to support 3d texture coords.
as for ply the naming of elements is not defined and therefore arbitrary
as for off and om these formats seem to only support 2d texcoords
stl seems to not support texcoords at all


See merge request !45
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