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/ExPolygonCollection.cpp

@@ -1,5 +1,8 @@
 #include "ExPolygonCollection.hpp"
 #include "Geometry.hpp"
+#ifdef SLIC3RXS
+#include "perlglue.hpp"
+#endif
 
 namespace Slic3r {
 
@@ -67,4 +70,8 @@ ExPolygonCollection::convex_hull(Polygon* hull) const
     Slic3r::Geometry::convex_hull(pp, hull);
 }
 
+#ifdef SLIC3RXS
+REGISTER_CLASS(ExPolygonCollection, "ExPolygon::Collection");
+#endif
+
 }