More fixes for the CMS.
* Saving a new menu item now updates the client-side appropriately. Fixes #33.
* Saving a text node now updates the client-side appropriately. Fixes #29.
* The new menu-item button now activates the main application. Fixes #23.
* The save-page button now also saves the menu item. Fixes #34.
* PageTypes now pass the page_id to the template. Fixes #26.
* Fixed some small mistakes.