atgc-core-light: create a controller / engine for dynamic light management

[jbilcke]

we can only have a few instances of light at the same time, but we probably want to display many (thousand) of them for robots lights, jet flames, explosions etc..

either we implement light as shaders, like this:
http://iloveshaders.blogspot.fr/2011/04/implementing-basic-lights.html

or we use a managed pool of light: we teleport the real light instances to the nearest light "slots", in the current viewport

designing such algorithm sucks a bit, maybe we should just go for the shader solution, I don't know