Added Markdown editor and Javascript code refactoring

assets/js/src/BoardCollapsedMode.js

@@ -0,0 +1,25 @@
+Kanboard.BoardCollapsedMode = function(app) {
+    this.app = app;
+};
+
+Kanboard.BoardCollapsedMode.prototype.keyboardShortcuts = function() {
+    var self = this;
+
+    Mousetrap.bind("s", function() {
+        self.toggle();
+    });
+};
+
+Kanboard.BoardCollapsedMode.prototype.toggle = function() {
+    var self = this;
+    this.app.showLoadingIcon();
+
+    $.ajax({
+        cache: false,
+        url: $('.filter-display-mode:not([style="display: none;"]) a').attr('href'),
+        success: function(data) {
+            $('.filter-display-mode').toggle();
+            self.app.get("BoardDragAndDrop").refresh(data);
+        }
+    });
+};