clear_queue_non_current: Don't use isCurrent
Don't mess with $LOGNAME in nix-shell
Remove per-platform links from the job page

Having different builds within a job is obsolete (issue #60), one
should have different job per platform (e.g. build.x86_64-linux).
Remove the jobs status page

The per-system presentation doesn't make much sense any more given
issue #60.  It should be replaced by (say) a grid showing each job per
evaluation.
Don't show bogus last-checked times
Remove unused ActiveJobs source