[OpenSCAD] Fix projection for OCCT7.3

OCCT 7.3 did not work well when using a very large projection plane, so
this commit reduces the plane size to the minimum required for the cut
operation. It also performs some minor refactoring in anticipation of
the implementation of the true projection feature, and it removes the
last attempted fix, which proved unnecessary.

src/Mod/OpenSCAD/OpenSCADFeatures.py

@@ -434,15 +434,6 @@ class Twist:
 
                     auxiliary_spine = Part.makeHelix(pitch, height, radius, 0.0, left_handed)
 
-                    # OCC versions before 7.5 had a problem with using a helix as the auxilliary spine, so approximate
-                    # it piecewise
-                    occ_version = Part.OCC_VERSION.split(".")
-                    if int(occ_version[0]) <= 7 and int(occ_version[1]) < 5:
-                        num_points = int(max(3,num_revolutions * 36)) # Every ten degrees is adequate
-                        wire = auxiliary_spine.Wires[0]
-                        points = wire.discretize(Number=num_points)
-                        auxiliary_spine = Part.makePolygon(points)
-                    
                 faces = [lower_face,upper_face]
                 for wire1,wire2 in zip(lower_face.Wires,upper_face.Wires):
                     pipe_shell = Part.BRepOffsetAPI.MakePipeShell(spine)