Initial work for 3D rendering of toolpaths

xs/xsp/ExtrusionEntityCollection.xsp

@@ -28,6 +28,7 @@
         %code{% RETVAL = THIS->entities.empty(); %};
     std::vector<size_t> orig_indices()
         %code{% RETVAL = THIS->orig_indices; %};
+    Polygons grow();
 %{
 
 void

xs/xsp/ExtrusionLoop.xsp

@@ -31,6 +31,7 @@
     bool is_perimeter();
     bool is_infill();
     bool is_solid_infill();
+    Polygons grow();
 %{
 
 SV*

xs/xsp/ExtrusionPath.xsp

@@ -29,6 +29,7 @@
     std::string gcode(Extruder* extruder, double e, double F,
         double xofs, double yofs, std::string extrusion_axis,
         std::string gcode_line_suffix);
+    Polygons grow();
 %{
 
 ExtrusionPath*

xs/xsp/Line.xsp

@@ -33,6 +33,7 @@
     Polyline* as_polyline()
         %code{% RETVAL = new Polyline(*THIS); %};
     Clone<Point> normal();
+    Clone<Point> vector();
 %{
 
 Line*
@@ -79,4 +80,5 @@ Line::coincides_with(line_sv)
     Ref<Pointf3> b()
         %code{% RETVAL = &THIS->b; %};
     Clone<Pointf3> intersect_plane(double z);
+    void scale(double factor);
 };