Implement type checking for XS objects

Type handling is mainly done using templates.
Template Slic3r::ClassTraits is used to store info about exported types (perl class name). Currently only perl class name and refference name is used.
Template values are initialized by REGISTER_CLASS macro. This macro is used in .cpp file of class ( it needs to be used exactly for each type).

Ref<type> class is used to return value as perl reference. Operator overloading is used to make c++ and XSpp happy, only pointer value should be possible to return.

Clone<type> class is used to return copy of value ( using new and copy constructor). Copy is created on assigment, this should be probably improved (memory leak on multiple assignments).
It is overloaded to be able to return type, type* and type&.

Typechecking in ExtrusionEntityCollection updated to check all passed types.

xs/src/ExtrusionEntity.cpp

@@ -1,8 +1,11 @@
-#include <sstream>
 #include "ExtrusionEntity.hpp"
 #include "ExtrusionEntityCollection.hpp"
 #include "ExPolygonCollection.hpp"
 #include "ClipperUtils.hpp"
+#include <sstream>
+#ifdef SLIC3RXS
+#include "perlglue.hpp"
+#endif
 
 namespace Slic3r {
 
@@ -102,6 +105,9 @@ ExtrusionPath::_inflate_collection(const Polylines &polylines, ExtrusionEntityCo
 }
 
 #ifdef SLIC3RXS
+
+REGISTER_CLASS(ExtrusionPath, "ExtrusionPath");
+
 std::string
 ExtrusionPath::gcode(SV* extruder, double e, double F,
     double xofs, double yofs, std::string extrusion_axis,
@@ -212,4 +218,8 @@ ExtrusionLoop::last_point() const
     return this->polygon.points.front();  // in polygons, first == last
 }
 
+#ifdef SLIC3RXS
+REGISTER_CLASS(ExtrusionLoop, "ExtrusionLoop");
+#endif
+
 }