(#16429) Fix relative URLs of icons in tables.css

These links work when puppet-dashboard is at the top level because browsers treat /../ as equivalent to /.
(#16429) fix relative links in application.scss

With corresponding generated changes in application.css
(#16429) use a controller reference for the delayed jobs link

This gets the path right even when the app is hosted at a sub-URI.
A basic test of the page looks for the link.
(#16429) use correct links for radiator, too
Merge pull request #122 from djmitche/relpaths

(#16429) Relpaths