DBFBProfilePictureView

The control improves on a number of aspects of the Facebook SDK provided FBProfilePictureView. 1) Caching of the downloaded profile images, so the network does not get hit for every instance of the view. 2) Start and completion handlers to allow control of the presentation of the view (e.g. fade-in or show a UIActivityIndicatorView) 3) Be notified through the completion handler when an image download fails. 4) Control when the empty profile image is shown. 5) Work well when the view is embedded in a UITableCellView.