Export code (work in progress)

Details:
-set members to private
Export code (work in progress)

Details:
-fleshed out TextureParams
-added ColorSpectrum to represent the values of ColorAxis
-added SimplexTextureSource.getTextureParams
Export code (work in progress)

Details:
-moved ColorSpectrum and TextureParams from export
-added CombineParams
-added TextureData
-added TextureFunctions generate and combine
-refactored SimplexTextureSource to use TextureFunctions.generate
-refactored TextureCombiner to use TextureFunctions.combine