Mark as unread in Site Updates

There's been several requests for this one and it was reasonably easy to implement, so I did it. Now, if you click on an entry, start reading, then realize you need to come back to it later, just click the Unread button off to the right side of the entry title. It should reappear in your Unread bookmarks list.

EDIT: Many of you were quick to point out your newly acquired pages of old bookmarks. I added back in my original restriction to only show a week's worth of bookmarks in that list. Oops.