Refactor some parts of the Architecture:

* JSON visitor are located in the format namespace
  * Visitor are *real* visitor
  * Visitable class has been renamed to Object
  * Due to a bug in Visual Studio 2015, we move to VS2017

api/python/pyObject.cpp

@@ -0,0 +1,5 @@
+#include "pyLIEF.hpp"
+
+void init_LIEF_Object_class(py::module& m) {
+  py::class_<LIEF::Object>(m, "Object");
+}