Materials: External Modules Part 1

Refactored code to support local and external material sources

This is the first PR in a series to support external modules. External
modules allow materials to be stored in external data sources such as
databases or web services. No new functionality is introduced in this
PR, rather it is a refactoring of code that will allow for changes to
be introduced in future PRs. Minor performance improvements have also
been made in the model and material managers.

The Python API has been enhanced for many data types to allow for
modification within Python.

src/Mod/Material/App/PyVariants.cpp

@@ -0,0 +1,75 @@
+/***************************************************************************
+ *   Copyright (c) 2023 David Carter <dcarter@david.carter.ca>             *
+ *                                                                         *
+ *   This file is part of FreeCAD.                                         *
+ *                                                                         *
+ *   FreeCAD is free software: you can redistribute it and/or modify it    *
+ *   under the terms of the GNU Lesser General Public License as           *
+ *   published by the Free Software Foundation, either version 2.1 of the  *
+ *   License, or (at your option) any later version.                       *
+ *                                                                         *
+ *   FreeCAD 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      *
+ *   Lesser General Public License for more details.                       *
+ *                                                                         *
+ *   You should have received a copy of the GNU Lesser General Public      *
+ *   License along with FreeCAD. If not, see                               *
+ *   <https://www.gnu.org/licenses/>.                                      *
+ *                                                                         *
+ **************************************************************************/
+
+#include "PreCompiled.h"
+
+#include <QVariant>
+
+#include "PyVariants.h"
+#include "Exceptions.h"
+
+using namespace Materials;
+
+PyObject* Materials::_pyObjectFromVariant(const QVariant& value)
+{
+    if (value.isNull()) {
+        Py_RETURN_NONE;
+    }
+
+    if (value.userType() == qMetaTypeId<Base::Quantity>()) {
+        return new Base::QuantityPy(new Base::Quantity(value.value<Base::Quantity>()));
+    }
+    if (value.userType() == QMetaType::Double) {
+        return PyFloat_FromDouble(value.toDouble());
+    }
+    if (value.userType() == QMetaType::Float) {
+        return PyFloat_FromDouble(value.toFloat());
+    }
+    if (value.userType() == QMetaType::Int) {
+        return PyLong_FromLong(value.toInt());
+    }
+    if (value.userType() == QMetaType::Long) {
+        return PyLong_FromLong(value.toInt());
+    }
+    if (value.userType() == QMetaType::Bool) {
+        return Py::new_reference_to(Py::Boolean(value.toBool()));
+    }
+    if (value.userType() == QMetaType::QString) {
+        return PyUnicode_FromString(value.toString().toStdString().c_str());
+    }
+    if (value.userType() == qMetaTypeId<QList<QVariant>>()) {
+        return Py::new_reference_to(getList(value));
+    }
+
+    throw UnknownValueType();
+}
+
+Py::List Materials::getList(const QVariant& value)
+{
+    auto listValue = value.value<QList<QVariant>>();
+    Py::List list;
+
+    for (auto& it : listValue) {
+        list.append(Py::Object(_pyObjectFromVariant(it)));
+    }
+
+    return list;
+}