use device orientation rather than status bar orientation

In some cases, we may be using neither "Auto Layout" nor "Springs and Struts", and may instead be completely managing our layouts programatically. For example, if we wanted to replicate the behavior of Apple's camera app where the "record" button is always fixed to the bottom of the _device_ rather than the bottom of the _view_. In these cases, we want to use the orientation of the _device_ rather than the orientation of the status bar.