Implement removed DeltaScript native functions as API functions

[jbunke]

• [x] $Graphics.gen_lookup(image source, bool dim) -> image
• [x] $Graphics.uv_mapping(image texture, image map, image animation) -> image

[jbunke]

Additional

• [x] $Graphics.light_mask(image source, float luminosity, float radius) -> image
• [x] $Graphics.lerp_color(color a, color b, float t) -> color