Make scenes loadable from files

[GoogleCodeExporter]

Something similar to shaders model JSON definition file, but for the 
scene graph. First definitions can include: visible objects, with stati
c position, or jBullet simulated, some geometry (linking it to 
physics world could be interesting), and Material definition. Later lights 
ans other stuff can come in.

Original issue reported on code.google.com by yinotaurus on 19 Feb 2011 at 3:50