1) All slicer's exceptions are now derived from Slic3r::Exception.
2) New exceptions are defined for slicing errors.
3) Exceptions are propagated to the Plater to show.
It remains to modify the slicing back-end to throw the new SlicingError
exceptions instead of std::runtime_error and to show the other exceptions
by a message dialog instead of a notification.
BoundingBox constructor will no more throw for empty vector of points.
GMP allowed for Vojtech's fork of boost::polygon Voronoi implementation.
Added libslic3r tests for boost::polygon Voronoi. All Voronoi issues
ever reported on the Internet are captured by the tests. Two issues
reported (the two test cases) are real issues which may influence
PrusaSlicer negatively, namely
https://github.com/boostorg/polygon/issues/43
Lazy "Place on face" gizmo update.
Caching of MeshObject::raw_mesh_bounding_box() for the object size display.
ModelObject::bounding_box(), raw_mesh_bounding_box(), full_raw_mesh_bounding_box() will not copy the mesh.
TriangleMesh::transformed_bounding_box(const Transform3d &trafo) will not copy the mesh data.
get_options_for_bundle() will not return reference to temp value
is_splittable() calls cheap mesh.has_multiple_patches()
