Refactored out the executor. Reverting to bash by default.
Refactored out the executor. Reverting to bash by default.

drlagos/mpisessions-playpen,cogumbreiro/sepi-playpen,drlagos/mpisessions-playpen,drlagos/unify-playpen,cogumbreiro/sepi-playpen,cogumbreiro/scribble-playpen,cogumbreiro/scribble-playpen,cogumbreiro/scribble-playpen,drlagos/unify-playpen