Feature/basic osg shader

rebased
That file not used anymore, should be removed.

 Note that TextureMaterial 'equivalent' is a relatively cryptic undocumented struct {variable: ..; textureUnit: } in the Compiler.js _texturesByName().

Have to find a way to make that explicit/documented  
( see for instance https://github.com/cedricpinson/osgjs/blob/feature/basicOsgShader/sources/osgShader/shaderGenerator/Compiler.js#L77 but other occurence in the file)