Implement light scene nodes.

[GoogleCodeExporter]

All scene lights should be defined in scene graph. Instead, now there is only 
one hard-coded light in the scene. Current limited shaders support only one 
light. (These two problems doesn't block each other.)

A Scene Light should contain at least:
1. Ambient, Diffusive, Specular and Shininess components
2. Attenuation (Fade-off) function
3. Position and/or Direction, Shape (spot cut-off)

Lights should be turned off for static objects, if they have shadow maps 
defined. Shadow maps have to be implemented in a separate issue. 

Original issue reported on code.google.com by yinotaurus on 16 Dec 2010 at 9:54

[GoogleCodeExporter]

Revision #21 has some code implemented and now this is blocked on Shaders

Original comment by yinotaurus on 21 Dec 2010 at 1:01

• Changed state: Accepted

[GoogleCodeExporter]

Shaders don't block the light nodes anymore. I have directional and point 
lights working in my sources. Let's put the Machine on Sun light. :)

Original comment by yinotaurus on 13 Feb 2011 at 9:54

• Changed state: Started

[GoogleCodeExporter]

Well, I unified all the GLs light models now in one class 
<code>GenericLightSceneNode</code>. The actual light type (directional, point, 
spot) is determined by a new enum. The lighting shader got many improvements 
and some bug have been fixed as a side effect. 

Original comment by yinotaurus on 19 Feb 2011 at 3:17

• Changed state: Fixed