Light related core functions

[jfacorro]

• ambient - "Sets the ambient reflectance for shapes drawn to the screen"
• ambient-light - "Adds an ambient light"
• directional-light - "Adds a directional light"
• emissive - "Sets the emissive color of the material used for drawing shapes drawn to the screen"
• light-falloff - "Sets the falloff rates for point lights, spot lights, and ambient lights"
• light-specular - "Sets the specular color for lights"
• lights - "Sets the default ambient light, directional light, falloff, and specular values"
• no-lights - "Disable all lighting"
• point-light - "Adds a point light"
• shininess - "Sets the amount of gloss in the surface of shapes"
• specular - "Sets the specular color of the materials used for shapes drawn to the screen, which sets the color of hightlights"
• spot-light - "Adds a spot light"