Fixed various issues in the ported Lightning infill.

Added export to SVG for TreeNode.
Also was finalized integration of Lightning infill and Lightning infill was enabled.

src/libslic3r/Print.hpp

@@ -35,7 +35,13 @@ namespace FillAdaptive {
     struct Octree;
     struct OctreeDeleter;
     using OctreePtr = std::unique_ptr<Octree, OctreeDeleter>;
-};
+}; // namespace FillAdaptive
+
+namespace FillLightning {
+    class Generator;
+    struct GeneratorDeleter;
+    using GeneratorPtr = std::unique_ptr<Generator, GeneratorDeleter>;
+}; // namespace FillLightning
 
 // Print step IDs for keeping track of the print state.
 // The Print steps are applied in this order.
@@ -387,6 +393,7 @@ private:
     void combine_infill();
     void _generate_support_material();
     std::pair<FillAdaptive::OctreePtr, FillAdaptive::OctreePtr> prepare_adaptive_infill_data();
+    FillLightning::GeneratorPtr prepare_lightning_infill_data();
 
     // XYZ in scaled coordinates
     Vec3crd									m_size;