Parallelization of stopping criteria ||residual|| < epsilon

[mdavezac]

Could be done locally ||residual_i|| < epsilon_i, and the result aggregated, or the residual aggregated and compared to a global epsilon.

[Luke-Pratley]

This has been done with local and global convergence functions in the convergence function factory. The same was done with the convergence of the Dual Forward Backward algorithm in ADMM.