Added list<blk_ref> template to SWIG file.

pyniflib.i

@@ -38,6 +38,7 @@ POSSIBILITY OF SUCH DAMAGE. */
 %include "stl.i"
 %include "std_map.i"
 %include "exception.i"
+%include "std_list.i"
 
 %exception {
     try {
@@ -63,6 +64,7 @@ struct Key {
 %template(vector_float) std::vector<float>;
 %template(vector_blk_ref) std::vector<attr_ref>;
 %template(vector_blk_ref) std::vector<blk_ref>;
+%template(list_blk_ref) std::list<blk_ref>;
 %template(vector_Vector3) std::vector<Vector3>;
 %template(vector_Color) std::vector<Color>;
 %template(vector_UVCoord) std::vector<UVCoord>;