Adds default template for examples
Disable frsustrum culling by default because of https://github.com/cedricpinson/osgjs/issues/74
Adds pbr sample
Setup initial sample with environments
Adds model and reorganize sample code
Adds texture unito 0
Should work with based importance sampling but it does not
Test importance sampling
Needs now to filter correctly the lod
Uses roughness on multi texture because of lod issue
Add a new model and configure the environments
Fixes camera position
Adds new model from allego
Adds template scene with metallic materials
Adds environments
Adds glsl texture function to use prefiltered environment
Adds script to build ibl
Adds new map generated by offline tools

The specular ibl contains inline mipmap. Diffuse and specular are
encoded with rgbm.
the integrate texture is a lut roughness/NoV packed into 16bits values
in rgba.
Dont take mipmap lower a given resolution
Added the reference rendering to switch from both rendering

envmap are not well generated I need to update the computing because
the roughness range is truncated for low value of roughness.
Still I am not sure that the reference rendering is good, it seems a bit
too shiny.