Merge: Noise generators: Perlin and interpolated

Intro the PerlinNoise generator and the underlying (but independent) InterpolatedNoise, with some related services.

The rosetta code Perlin noise example (in 3D) is for comparison to my implementation in `lib/noise.nit` in (2D). We do not get the expected result with this implementation, 0.13691995878400010 vs 0.13691995878400012. It may be an error in the implementation of `Float.to_precision`... this will require further investigation.

The optimized `SequenceRead::rand` is a bonus! it is not used in this PR.

Pull-Request: #1194
Reviewed-by: Jean Privat <jean@pryen.org>
Reviewed-by: Alexandre Terrasa <alexandre@moz-code.org>
Reviewed-by: Lucas Bajolet <r4pass@hotmail.com>