Total refactoring

• Removed the BCCNoise functions.
• Rewrote the webgl-noise functions to use more modern and simpler way to generate gradients.
• Function renaming: snoise -> SimplexNoise, cnoise -> ClassicNoise, pnoise -> PeriodicNoise
• Added include guards. Now you can use these shaders without conflicts.
• Changed the normalization coefficients. Now these noise functions return values roughly fit in [-1, +1].