Reworked the Perl unit / integration tests to use the same Print

interface that the application is using. Old interface used just
for the integration tests was removed.

xs/xsp/Model.xsp

@@ -211,6 +211,7 @@ ModelMaterial::attributes()
     void set_origin_translation(Vec3d* point)
         %code%{ THIS->origin_translation = *point; %};
     
+    void ensure_on_bed();
     bool needed_repair() const;
     int materials_count() const;
     int facets_count();