ECOM-1339 Branding API footer

Serve branded footer JSON/HTML/CSS/JS from an API endpoint
in the branding app.  Refactor OpenEdX and EdX.org footer templates
to use the Python version of the API, ensuring that the API
values are consistent with the footer included in main.html.

Detailed changes:

* Added footer API end-point to the branding app.
* Footer API allows the language to be set with querystring parameters.
* Footer API allows showing/hiding of the OpenEdX logo using querystring parameters.
* Deprecate ENABLE_FOOTER_V3 in favor of the branding API configuration flag.
* Move no referrer script into main.html from the edx footer template.
* Rename rwd_header_footer.js to rwd_header.js
* Cache API responses.

Authors:
Awais Qureshi, Aamir Khan, Will Daly

common/static/js/spec_helpers/rwd_header_footer.js

@@ -1,99 +0,0 @@
-/**
- * Adds rwd classes and click handlers.
- */
-
-(function($) {
-    'use strict';
-
-    var rwd = (function() {
-
-        var _fn = {
-            header: 'header.global-new',
-
-            footer: '.edx-footer-new',
-
-            resultsUrl: 'course-search',
-
-            init: function() {
-                _fn.$header = $( _fn.header );
-                _fn.$footer = $( _fn.footer );
-                _fn.$nav = _fn.$header.find('nav');
-                _fn.$globalNav = _fn.$nav.find('.nav-global');
-
-                _fn.add.elements();
-                _fn.add.classes();
-                _fn.eventHandlers.init();
-            },
-
-            add: {
-                classes: function() {
-                    // Add any RWD-specific classes
-                    _fn.$header.addClass('rwd');
-                    _fn.$footer.addClass('rwd');
-                },
-
-                elements: function() {
-                    _fn.add.burger();
-                    _fn.add.registerLink();
-                },
-
-                burger: function() {
-                    _fn.$nav.prepend([
-                        '<a href="#" class="mobile-menu-button" aria-label="menu">',
-                            '<i class="icon fa fa-reorder" aria-hidden="true"></i>',
-                        '</a>'
-                    ].join(''));
-                },
-
-                registerLink: function() {
-                    var $register = _fn.$nav.find('.cta-register'),
-                        $li = {},
-                        $a = {},
-                        count = 0;
-
-                    // Add if register link is shown
-                    if ( $register.length > 0 ) {
-                        count = _fn.$globalNav.find('li').length + 1;
-
-                        // Create new li
-                        $li = $('<li/>');
-                        $li.addClass('desktop-hide nav-global-0' + count);
-
-                        // Clone register link and remove classes
-                        $a = $register.clone();
-                        $a.removeClass();
-
-                        // append to DOM
-                        $a.appendTo( $li );
-                        _fn.$globalNav.append( $li );
-                    }
-                }
-            },
-
-            eventHandlers: {
-                init: function() {
-                    _fn.eventHandlers.click();
-                },
-
-                click: function() {
-                    // Toggle menu
-                    _fn.$nav.on( 'click', '.mobile-menu-button', _fn.toggleMenu );
-                }
-            },
-
-            toggleMenu: function( event ) {
-                event.preventDefault();
-
-                _fn.$globalNav.toggleClass('show');
-            }
-        };
-
-        return {
-            init: _fn.init
-        };
-    })();
-
-    setTimeout( function() {
-        rwd.init();
-    }, 100);
-})(jQuery);

common/static/js/utils/rwd_header.js

@@ -10,6 +10,7 @@
         var _fn = {
             header: 'header.global-new',
 
+            // TODO (ECOM-1339): Remove this once the V3 footer is enabled permanently
             footer: '.edx-footer-new',
 
             resultsUrl: 'course-search',
@@ -29,7 +30,7 @@
                 classes: function() {
                     // Add any RWD-specific classes
                     _fn.$header.addClass('rwd');
-                    _fn.$footer.addClass('rwd');
+                    _fn.$footer.addClass('rwd');  // TODO (ECOM-1339): remove once the V3 footer is enabled permanently
                 },
 
                 elements: function() {