Light structure redundancy

[AlexandreLamure]

Avoid declaring the light structures (Material, DirLight, PointLight) in all.glsl.

[AlexandreLamure]

It does not seem to be possible currently.
struct cannot be forward declared.
The best solution would be to merge compute_lights in all.glsl.

[AlexandreLamure]

An other solution would be to edit the all.glsl file using C++ code.
Using this solution, we could also edit the preprocessor constants in compute-lights.glslto set variable length of array.