Base: Rename Base::freecad_dynamic_cast into freecad_cast

This is to make it shorter and easier to use. QT does the same thing
with their qobject_cast.

src/Gui/DemoMode.cpp

@@ -145,7 +145,7 @@ void DemoMode::hideEvent(QHideEvent*)
 Gui::View3DInventor* DemoMode::activeView() const
 {
     if (Document* doc = Application::Instance->activeDocument()) {
-        return Base::freecad_dynamic_cast<Gui::View3DInventor>(doc->getActiveView());
+        return freecad_cast<Gui::View3DInventor>(doc->getActiveView());
     }
 
     return nullptr;