Removal of AmbientLight

The ambient light object has been removed as it didn't make sense how it works. Now, you can set a "Global Ambient" value in LightState using setGlobalAmbient.

The ambient values from other lights (point, directional, spot) will combine with the global for the final color.

When a lightstate has only the ambient light it was disabled due to the condition

if (quantity > 0 && isEnabled())

in LWJGLLightState. I changed that to

if (isEnabled())