support import/export in kanban

www/kanban/inner.js

@@ -326,7 +326,21 @@ define([
 
         if (framework.isReadOnly()) {
             $container.addClass('cp-app-readonly');
+        } else {
+            framework.setFileImporter({}, function (content, file) {
+                var parsed;
+                try { parsed = JSON.parse(content); }
+                catch (e) { return void console.error(e); }
+                return { content: parsed };
+            });
         }
+
+        framework.setFileExporter('json', function () {
+            return new Blob([JSON.stringify(kanban.getBoardsJSON())], {
+                type: 'application/json',
+            });
+        });
+
         framework.onEditableChange(function (unlocked) {
             if (framework.isReadOnly()) { return; }
             if (!kanban) { return; }