Zuul status page: support for progress bar

Copy pasted from http://status.openstack.org/zuul/ which shows the
progress of jobs while they are being run by Jenkins.  The new Zuul
version provides the elapsed and remaning time for a job which are
passed to a HTML5 <progress> element.

The functions comes as-is from Openstack:

 ssh://review.openstack.org:29418/openstack-infra/config.git
 modules/openstack_project/files/zuul/status.js

I have adapted them to pass jshint and use the object oriented style we
are using.

<progress> styling is a mess since each browser behave a bit
differently. Tested out on Chromium/Safari/Firefox. Hopefully IE is
right.

Tested locally seems good for me. Might want to deploy and adjust later.

Change-Id: Iff472abbbd7815ce328291b11dc5c1173c9c5951