Supersede ``PMDualNumber`` and ``PMHyperDualNumber`` classes by a ``PMMultiDualNumber`` class

[SergeStinckwich]

Dual numbers and hyper dual numbers are just specific examples of multi-dimensional dual numbers. I guess that later we can supersede PMDualNumber and PMHyperDualNumber classes by a PMMultiDualNumber class later like the one used in ForwardDiff.jl: https://github.com/JuliaDiff/ForwardDiff.jl