Currently, if you click on a menu item, current outstanding ajax requests are not aborted, and the new page will only load after the previous ajax requests have returned (depending on the browser concurrent connexion settings, etc.).

The most common use case is:

• open Piwik
• while dashboard is loading (many http requests queued)... user clicks on a different menu item
• The report displays 'loading...' but the numerous dashboard http requests are still being processed.
• the report user requested finally loads

Instead, when clicking on a menu item, all previous ajax requests should be cancelled and the new Ajax requests for the requested report should load directly.