Add webathena authentication button for Zephyr users.

This shows up when you're not running a Zephyr mirroring bot and lets
you use Webathena to have us run it.  Obviously needs more docs.

Current problems include:

* supervisorctl reload ends up recreating /var/run/supervisor.sock
  with the wrong permissions, so it only works once in a row before
  you need to chmod that.

* /etc/supervisor/conf.d needs to be humbug-writeable; this is a clear
  local root vulnerability

* This uses SSH and thus is kinda slow.

(imported from commit 7029979615ffd50b10f126ce2cf9a85a5eefd7a2)

zproject/settings.py

@@ -358,6 +358,7 @@ JS_SPECS = {
             'third/jquery-autosize/jquery.autosize.js',
             'third/lazyload/lazyload.js',
             'third/spectrum/spectrum.js',
+            'third/winchan/winchan.js',
             ('third/handlebars/handlebars.runtime.js'
                 if PIPELINE
                 else 'third/handlebars/handlebars.js'),