Added osgGA::Device class for integration of both physical and virtual devices.

Added template readFile(..) function to make it more convinient to cast to a specific object type.

Added support for osgGA::Device to osgViewer.

Added sdl plugin to provides very basic joystick osgGA::Device integration.

src/osgPlugins/sdl/ReaderWriterSDL.cpp

@@ -0,0 +1,38 @@
+// Released under the OSGPL license, as part of the OpenSceneGraph distribution.
+//
+// ReaderWriter for sgi's .rgb format.
+// specification can be found at http://local.wasp.uwa.edu.au/~pbourke/dataformats/sgirgb/sgiversion.html
+
+#include <osg/Notify>
+
+#include <osgDB/FileNameUtils>
+#include <osgDB/Registry>
+
+#include "JoystickDevice.h"
+
+
+class ReaderWriterSDL : public osgDB::ReaderWriter
+{
+    public:
+
+        ReaderWriterSDL()
+        {
+            supportsExtension("sdl","SDL Device Integration");
+        }
+
+        virtual const char* className() const { return "SDL Device Integration plugin"; }
+
+        virtual ReadResult readObject(const std::string& file, const osgDB::ReaderWriter::Options* options =NULL) const
+        {
+            if (file=="joystick.sdl")
+            {
+                return new JoystickDevice;
+            }
+            return ReadResult::FILE_NOT_HANDLED;
+        }
+
+};
+
+// now register with Registry to instantiate the above
+// reader/writer.
+REGISTER_OSGPLUGIN(sdl, ReaderWriterSDL)