Update PSTCollectionView.

Previous version had a crashing bug when dismissing a popup containing a
PSTCollectionView whose delegate was presented in the popup.
Move AwfulActionSheet into its own group.
Iconified action sheet.
Reorder thread actions so first/last page are on left.
Add "Copy URL" thread action to long-tap menu.
Centralize icon action items.
Iconify posts view thread actions.