Add basic status HTML/JS.

A working example that can be customized for site use.

Change-Id: I6e6fdf245a55a767aa7e86486b6c47dae221f47b
Reviewed-on: https://review.openstack.org/19989
Approved: James E. Blair <corvus@inaugust.com>
Reviewed-by: James E. Blair <corvus@inaugust.com>
Tested-by: Jenkins
Update zuul doc to cover SIGUSR1 behavior.

Change-Id: I6dcd87a59d836dc22b67a2bee7c764e0b603a809
Reviewed-on: https://review.openstack.org/21543
Approved: Jeremy Stanley <fungi@yuggoth.org>
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Tested-by: Jenkins