#1276

sos execute needs to know what executor to use. Giving that most tasks are submitted by the sos-pbs module with a template-generated bash file similar to

%PBS ..

sos execute {tasks}

it is most natural to change the template to something like

%PBS...

sos execute -e pbs {tasks}

So that sos execute can look for an executor called pbs and use it to execute specified tasks.

It is possible to let the pbs task engine to do some magic but making the option explicit seems to be better and allows easier testing.