modifiers in solver

Hi everyone,

I would like to add some modifiers to the solver used by a Formulation (modified Gram-Schmidt in gmres in that particular case).

I also would like to be independent from petsc (i.e. I'd like to avoid adding -ksp_gmres_modifiedgramschmidt).

An idea could be to add some sort of "mini language" to the solver string when calling Formulation::solve(...). For instance,

1. Formulation::solve("gmres", ...) starts gmres with classical Gram-Schmidt and
2. Formulation::solve("gmres+mgs", ...) starts gmres with modified Gram-Schmidt.

What do you think?

Have a nice weekend, Nicolas.