Add 'run time' to the jobs page

The 'jobs' page (e.g., https://autolab.encs.vancouver.wsu.edu/courses/swtest-s19/jobs) shows recently submitted jobs. The 'elapsed (s)' column measures time from submission until completion. It would also be great to have a column that measures the time used by the autograder. If a regrade is done, there will be a big queue, but it would be nice to know which submissions are taking a long time and that's currently hard to know.