TXna Game Engin 0.4.3 released

After a couple of long coding months we finally released the 0.4.3 version of the TXna Game Engine. There are major changes some of them breaking like switching to the new XNA 3.1 framework. Most of the changes are fixes and new features, there is even a PhysX integration demonstration in the Tutorial05.

BREAKING CHANGES:
- NEW XNA 3.1 version !!! You must download & install the Xna 3.1 framework before loading the solution
- removed Effect property from the RenderableSceneNode, added new Material property which contains the Effect property

NEWS:
- massive source refactoring
- new material system, the material is now a base for everything, it holds light data, effects, textures etc.
- completely rewritten the lightning data structures (shader + GenericEffect + SceneManager)
- added SceneLights class
- added Spot light support
- initial PhysX support via eyecm.PhysX.dll - the Candy PhysX .NET wrapper
- added ModelSceneNode support for the TXna build in GenericEffect (now models are lit and fogged the standard TXna way)
- added new SceneNodeOrdering enum for transparent nodes
- added RenderShadows engine property
- added ShadowMapRenderer class. Not finished yet.
- added 05Tutorial with PhysX integration demonstration. To run it the PhysX system software 2.8.1 must be installed!
- changed GenericEffect to adjust for the new lightning data
- changed, RenderableSceneNode.Draw() and in all inherited scene nodes: removed parameter LightInfo
- changed default UpdateOrder of BillboardSceneNode, set to TransparentNode from the default SceneNode.
- changed CameraSceneNode cached cameras bounding frustum and recreated in UpdateViewMatrix()
- fixed CubeSceneNode uv mapping, actually it is impossible to correctly map uv coordinates to all 6 box sides with only 8
vertices so 4 new vertices are added at the same position as back face vertices and used for top & bottom sides uv
- fixed directional light shading where the lights position was wrongly used instead of its direction
- fixed specular color for spot and point light calculations in Lights.fx
- fixed rendering transparent nodes after all other nodes ("transparent" = nodes with UpdateOrder==4, nothing to do with real
transparency). Still some glitches may occur with transparent nodes in front of other transparent nodes. This can be solved
only by sorting nodes after every camera move/rotation, and rendering back to front in regard to camera - which is expensive.
- updated all old tutorials