Remember sidebar section state when browsing the wiki

So we do not have to open the same section of the sidebar every time, we click
 a link to a new page.
It forgets the toggle-state if the content is manually or automatically
widened, for example by clicking on an edit-button.

SPR-883

js/sidebar.js

@@ -11,6 +11,20 @@ jQuery(function () {
     var setWideContent = function () {
             $nav.find('div.nav-panel').hide(); // close all panels
             jQuery('body').addClass('wide-content');
+            removeToggleStorage();
+        },
+
+        /**
+         * removes information about the toggle-state
+         */
+        removeToggleStorage = function () {
+            for (var index=0; index <= sessionStorage.length; index += 1) {
+                var item = sessionStorage.getItem('sidebar-section-' + index + '-open');
+                if (!item) {
+                    break;
+                }
+                sessionStorage.removeItem('sidebar-section-' + index + '-open');
+            }
         },
 
         /**
@@ -46,6 +60,7 @@ jQuery(function () {
                     focusFirstSubLink($panel);
                 }
             });
+            sessionStorage.setItem('sidebar-section-' + $toggler.data('index') + '-open', !isOpen);
         },
 
         /**
@@ -57,9 +72,13 @@ jQuery(function () {
             var $main = $nav.find('nav.nav-main');
             if (!$main.length) return;
 
+            if(jQuery('body').hasClass('wide-content')) {
+                removeToggleStorage();
+            }
+
             var ELEMENT = JSINFO.template.sprintdoc.sidebar_toggle_elements;
             var $elements = $main.find(ELEMENT);
-            $elements.each(function () {
+            $elements.each(function (index) {
                 var $me = jQuery(this),
 
                 // prepare text and the optional icon
@@ -83,6 +102,7 @@ jQuery(function () {
                         .text(text)
                         .wrapInner('<span class="lbl">')
                         .prepend($icon)
+                        .data('index', index)
                     ;
 
                 // wrap all following siblings til the next element in a wrapper
@@ -102,6 +122,11 @@ jQuery(function () {
                 if ($toggler.parent('li').length) {
                     $toggler.parent('li').addClass('toggler');
                 }
+
+                if (sessionStorage.getItem('sidebar-section-' + index + '-open') === 'true') {
+                    $wrap.css('display', 'block');
+                }
+
             });
         },