Add backup for nwchem handler. Improve handling of convergence errors. Now the run will skip past tasks which cannot be converged with cgmin.
Add backup for nwchem handler.
Improve handling of convergence errors. Now the run will skip past tasks which
cannot be converged with cgmin.

specter119/custodian,materialsproject/custodian,materialsproject/custodian,davidwaroquiers/custodian,specter119/custodian,materialsproject/custodian,specter119/custodian,alberthxf/custodian,xhqu1981/custodian