[#671] support_url setting for top navigation.

The link used for the Support navigation item can be customised in a
site's settings file by adding a row for `support_url` with a url as
value. If absent, the Support link will default to the instance-wide
`discussion_forum` value.

census/views/base.html

@@ -47,7 +47,9 @@
         {% if site.settings.tutorial_page %}
         <li><a href="/tutorial/">{{gettext("Tutorial")}}</a></li>
         {% endif %}
-        {% if discussionForum %}
+        {% if site.settings.support_url %}
+          <li><a target="_blank" href="{{ site.settings.support_url }}">{{ gettext("Support") }}</a></li>
+        {% elif discussionForum %}
           <li><a target="_blank" href="{{ discussionForum }}">{{ gettext("Support") }}</a></li>
         {% endif %}
       </ul>

fixtures/site.js

@@ -13,7 +13,8 @@ var objects = [
         reviewers: ['email1@example.com', 'email3@example.com'],
         'custom_footer': '<span style="display: none;">Custom footer</span>',
         'custom_css': '/* Custom CSS rules */',
-        'navbar_logo': '<span style="display: none;">Custom navbar logo</span>'
+        'navbar_logo': '<span style="display: none;">Custom navbar logo</span>',
+        'support_url': 'https://discuss.okfn.org/c/open-data-index/australia-index'
       }
     }
   },

tests/app.js

@@ -94,7 +94,8 @@ describe('Basics', function() {
           this.browser.visit('/', () => {
             assert.ok(this.browser.success);
             var html = this.browser.html();
-            _.forEach(['custom_css', 'navbar_logo', 'custom_footer'],
+            _.forEach(['custom_css', 'navbar_logo',
+                       'custom_footer', 'support_url'],
               settingName => {
                 var textToCheck = site.settings[settingName];
                 assert.include(html, textToCheck);