Encapsulate Arnoldi iteration

[jhabriel]

Lines 280 -- 298 from pd_gmres should be encapsulated into:

[H, W] = modified_gram_schmidt_arnoldi(A, v, m)

% Inputs:
%
% A: matrix n-by-n
% v: normalised residual vector
% m: restart parameter
%
% Outputs:
% W: Orthonormal basis of Krylov subspace
% H: Upper Hessenberg matrix
%

[gusespinola]

https://en.wikipedia.org/wiki/Arnoldi_iteration

[jhabriel]

Note to self:

I just realised that the normalised residual vector v is used after the Arnoldi block. This means that we need to return it as an output.

We need to discuss how to incorporate this as part of the modified_gram_schmidt_arnoldi.