Simplifies ShaderGraph inputs/outputs

- Now it's clear that nodes should not be helper
- Node must have input/output
- it's still not clear how to organize helpers in Compiler.js
Cleans new factory node system

- move gl_FragColor into data.js
- remove unused variable in Compiler
- fix registering of node in factory
Updates shader generator example
Fixes bug in Compiler

- fixes regexp issue in InlineCode
- add getAttributeType in Compiler
Simplifies code using getAttributeType
Fixes diffuseColor in lighting
Improves a little bit the shader node management
Updates gitignore
Changes the default behaviour when there is no lights
Merge pull request #193 from cedricpinson/feature/simplify-shader-generator-api

Feature/simplify shader generator api