Made tab views for outstanding items and overdue milestones

I separated the Overdue Milestones and Outstanding Items to tab views and made Overdue Milestones the default tab.

Having both on the same page is confusing, and when the Overdue Milestones gets long, that table pushes the Items too far down. Toggle hide/show for Overdue Milestones without state-saving is just as irksome as tab view, because user will have to keep closing the table to hide.

With the Overdue Milestones tab view as default will make people address the issue and hopefully deal with it to make the tab go away. This is a more effective habit changer.