Fix sorted tables with Bootstrap 4
    
    These sorted tables were in kinda rough shape since the move
    to fedora-bootstrap. This pulls in a newer version of the
    currently-maintained fork of tablesorter:
    
    https://github.com/Mottie/tablesorter
    
    which has Bootstrap 4 support, and uses it. This gives us sorted
    tables that actually work more or less right and have arrows
    and stuff. Also drop some of the weirder custom theming we had
    for these tables in the app CSS (why use thead-dark, but custom
    theme it to look almost identical to thead-light only with a
    silly gradient for some reason? Let's...not).
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>