Ascii was made the default format for the command gtsset and the gts2stl step is removed in pyformex_gts.boolean. A reader for binary gts format should still be added.

I noticed that the function `boolean` in pyformex_gts.py may return surfaces that are not manifold even if the input surfaces are manifolds. This function runs the `gtsset` command, which creates a binary GTS file and uses `gts2stl` to convert this binary file to STL format.

I looked at the code in pyformex/extra/gts/set.c and on line 332 there is `binary=TRUE`, which causes the output to be written to a binary GTS file, which can not be directly read into pyFormex. When changing this to `binary=FALSE` and ommitting the `gts2stl` filter command in `boolean`, my output surface is a manifold. Running the `gts2stl` command afterwards still returns a non-manifold. So probably this format conversion causes some nodes to be merged or so. Therefore, I suggest to write the output to ASCII format and to ommit the `gts2stl` command.