Merge branch 'master' into xsslice
Finished implementation of TriangleMesh->split
Implemented TriangleMesh->merge
Add unit test for split()
Make Repair() idempotent and lowercase
Ported TriangleMesh::scale_xyz()
Implemented TriangleMesh->clone
Replace TriangleMesh with the XS port
Round results when rotating to minimize errors & pass the tests
Calls to ->repair where needed
Incomplete work to store TriangleMesh objects in Model objects instead of extracting vertices and facets
More work to avoid working with vertices outside XS
clean use XXX
Read OBJ and AMF
Make plater work with new XS code
Use precomputed normals in 3D preview
Fix XS STL reader not populating stats.size correctly
Fix threads, tests and require the most recent Moo version
Merge pull request #1435 from jluis/master

Round results when rotating to minimize errors & pass the tests
Fix concentric infill and add regression test. #1432