public final void addNode(ShaderNode c) {
            if (!nodes.contains(c)) {
                nodes.add(c);
            }
        }
This class is here to be able to load shaderNodeDefinition from both the
J3MLoader and ShaderNodeDefinitionLoader.

It also allows loading shader nodes from a j3md file and building the
ShaderNodes list of each technique and the ShaderGenerationInfo needed to
generate shaders.

@author Nehon
jme3-core/src/plugins/java/com/jme3/material/plugins/ShaderNodeLoaderDelegate.java