Bug 801: Graph OpenGL ES2 and ES3 Compatibility

- Remove 'const' qualifier in shader graph code for non 'absolute' const values

- Use extension directive OES_standard_derivatives only for ES2.0, not ES3.0 (graph shader)

- Compare float w/ float literals, not int literals!

- Android Demo NEWTGraphUI2pActivity:
  - Is a VBAA example, hence disable scene MSAA!