Matlab and python interface exit status

[ctribes]

Both python and matlab interfaces should provide complete exit status range: % 1 - converged / target reached % 0 - maximum iterations / function evaluations exceeded % -1 - infeasible / mesh limit reached % -2 - initialization error % -3 - nomad error % -5 - user exit

This issue has been updated using issue #124. Maybe we need more exit statuses (and clarify the meaning):

• (feasible+max eval/iter reached) from (infeasible+max eval/iter reached).
• (feasible+mesh limit reached-> equivalent to 1-converged) from (infeasible+mesh limit reached).