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).