Plugin exports incorrect texture filenames

[sabra999]

This seems to be inconsistent behaviour.

When exporting to obj/fbx, the texture filenames are sometimes "scene_000.png", "scene_001.png" etc.

Try exporting and reopening within Noesis - sometimes the textures are preserved ("mat1_c", "mat1_r", "mat1_n" etc.) and all the textures are found/resolved on reopening. (test_file13-19 export properly).