Added Markdown editor and Javascript code refactoring

assets/js/src/BoardPolling.js

@@ -0,0 +1,33 @@
+Kanboard.BoardPolling = function(app) {
+    this.app = app;
+};
+
+Kanboard.BoardPolling.prototype.execute = function() {
+    if (this.app.hasId("board")) {
+        var interval = parseInt($("#board").attr("data-check-interval"));
+
+        if (interval > 0) {
+            window.setInterval(this.check.bind(this), interval * 1000);
+        }
+    }
+};
+
+Kanboard.BoardPolling.prototype.check = function() {
+    if (this.app.isVisible() && !this.app.get("BoardDragAndDrop").savingInProgress) {
+        var self = this;
+        this.app.showLoadingIcon();
+
+        $.ajax({
+            cache: false,
+            url: $("#board").data("check-url"),
+            statusCode: {
+                200: function(data) {
+                    self.app.get("BoardDragAndDrop").refresh(data);
+                },
+                304: function () {
+                    self.app.hideLoadingIcon();
+                }
+            }
+        });
+    }
+};