job_log and computation errors

[sunu]

Currently jobs/tasks that end with computation errors aren't logged anywhere locally. job_log_<project>.txt file, logs only jobs that end successfully.

For monitoring purposes it would be nice to have a log of jobs/tasks with computation errors, either in a separate file or in the same job_log_<project>.txt file adding a new field with exit code.

This would also reduce web traffic and project database queries for those who troubleshoot or like to monitor their account very closely.