[Enh] Real data perturbation algorithms

[JusteRaimbault]

Create synthetic datasets from real data through perturbations (one of the initial purposes of the library)

[JusteRaimbault]

This splits into

• real data import
• data perturbators

For the second point, see what was discussed within Dynamicity project: random perturbation of spatial fields, possibly correlated (pop/employments ~ urban projects) with controlled level of correlation; more generally one good entry for validation of Luti models (LU module)