Remove all of the Python downcasting framework

This should now happen behind the scenes in Boost Python.
Refs #9801

Code/Mantid/Framework/PythonInterface/inc/MantidPythonInterface/api/ExtractWorkspace.h

@@ -0,0 +1,43 @@
+#ifndef MANTID_PYTHONINTERFACE_EXTRACTWORKSPACE_H_
+#define MANTID_PYTHONINTERFACE_EXTRACTWORKSPACE_H_
+/**
+    Copyright © 2015 ISIS Rutherford Appleton Laboratory, NScD Oak Ridge
+   National Laboratory & European Spallation Source
+
+    This file is part of Mantid.
+
+    Mantid is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    Mantid is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+    File change history is stored at: <https://github.com/mantidproject/mantid>
+    Code Documentation is available at: <http://doxygen.mantidproject.org>
+*/
+#include <MantidAPI/Workspace.h>
+
+#include <boost/python/object_fwd.hpp>
+
+namespace Mantid {
+namespace PythonInterface {
+
+struct ExtractWorkspace {
+  ExtractWorkspace(const boost::python::object &pyvalue);
+  bool check() const;
+  const API::Workspace_sptr operator()() const;
+
+private:
+  API::Workspace_sptr m_value;
+};
+}
+}
+
+#endif // MANTID_PYTHONINTERFACE_EXTRACTWORKSPACE_H_

Code/Mantid/Framework/PythonInterface/inc/MantidPythonInterface/kernel/PropertyWithValueExporter.h

@@ -25,31 +25,30 @@
 */
 
 #include "MantidKernel/PropertyWithValue.h"
-#include "MantidPythonInterface/kernel/Policies/DowncastingPolicies.h"
 
 #ifndef Q_MOC_RUN
 #include <boost/python/class.hpp>
 #include <boost/python/bases.hpp>
 #include <boost/python/return_value_policy.hpp>
+#include <boost/python/return_by_value.hpp>
 #endif
 
 namespace Mantid {
 namespace PythonInterface {
 /**
  * A helper struct to export PropertyWithValue<> types to Python.
  */
-template <typename HeldType> struct PropertyWithValueExporter {
+template <typename HeldType, typename ValueReturnPolicy=boost::python::return_by_value>
+struct PropertyWithValueExporter {
   static void define(const char *pythonClassName) {
     using namespace boost::python;
     using namespace Mantid::Kernel;
 
     class_<PropertyWithValue<HeldType>, bases<Property>, boost::noncopyable>(
         pythonClassName, no_init)
-        .add_property(
-            "value",
-            make_function(
-                &PropertyWithValue<HeldType>::operator(),
-                return_value_policy<Policies::ToSharedPtrWithDowncast>()));
+        .add_property("value",
+                      make_function(&PropertyWithValue<HeldType>::operator(),
+                                    return_value_policy<ValueReturnPolicy>()));
   }
 };
 }