Fix crash deleting last favorite forum.

We need to reload the row before changing the favoriteForums array, otherwise
can get the wrong section in the update.

Bonus: unconditionally reload the row so the star appears or disappears as
appropriate.
Prevent following a link after a long press to show the share sheet.

Previous behavior on a long press was to show a UIActionSheet, which somehow
caused the UIWebView's gesture recognizers to fail. Now we need to mimic that
ourselves.
Factor out manually failing a UIGestureRecognizer.
Stiffen the swipe-to-show-sidebar gesture.