IterationInformation for stress state iterations

[KnutAM]

With the new parameterization of the iteration stress states, it would be possible to parameterize the stress state with an iteration debug output, such that if the users set this option on, the stress state iterations are logged (potentially with different options). Care must be taken to inflict no run-time performance hit for standard cases, a simple interface could be update_iteration_log!(stress_state, iter, σ_mandel, σ_full) which would be a no-op for non-logging states, and at the end / at no convergence print_iteration_log(stress_state) could be called (and be a no-op for non-logging states)