Ruled Surface: strips off an edge chain, exact where possible (#762) (#1151)

Ruled Surface: strips off an edge chain in normal, tangent, angle or direction mode, exact planes/cylinders/cones where possible, mitred or round corners, stitched into one surface body. SurfaceRuled is noted under format 21. Closes #762.

crates/kernel/src/lib.rs

@@ -94,6 +94,7 @@ mod step_in;
 mod step_out;
 mod surface_kind;
 mod surface_offset;
+mod surface_ruled;
 mod surface_untrim;
 mod surfaces;
 mod sweep_path;
@@ -138,6 +139,7 @@ pub use step_in::{ImportedBody, StepImport, StepNode, step_cache_alive, step_imp
 pub use step_out::{ExportBody, ExportProduct, StepHeader, step_export_bodies, step_export_products};
 pub use surface_kind::{FaceSurface, face_surface};
 pub use surface_offset::offset_surface;
+pub use surface_ruled::{Ruled, RuledCorners, RuledMode, ruled_surface};
 pub use surface_untrim::{UntrimHoles, untrim};
 pub use surfaces::{
     copy_faces, extend, extrude_sheet, loft_sheet, patch_edges, patch_region, remove_faces, reverse_faces, revolve_sheet, stitch, sweep_sheet,