[eigen] Interest in more initialisation methods for dynamic-size arrays/matrices

[Deanna Hood <deanna.m.hood@xxxxxxxxx>]

Hi everyone,

Has anyone else ever wanted to do 

Array2Xf x = Array2Xf::Random(5);  (i.e. only specify free-dim size)

instead of having to do 

Array2Xf x = Array<float, 2, 5>::Random(); ?

I've implemented the functionality to enable this (and for MatrixX3i::Zero(4), etc.) because an exception piqued my interest, and I am trying to see if it would be valuable to others and warrants a pull request.

Cheers,

Deanna