Issue/135: Don't silently pass through face up/down device orientations

[frosty]

Fixes #135.

The camera preview image was getting flipped when holding the device in portrait and then tilting it forward (as though you were going to point it downwards). This seemed to be because we were casting UIDeviceOrientation directly to AVCaptureVideoOrientation, but AVCaptureVideoOrientation has two extra Face Up / Face Down cases that the AV enum doesn't have. To fix the issue, we convert either of those cases to AVCaptureVideoOrientationPortrait.

To test:

• Run on a device
• Open the picker and look at the camera preview cell
• Hold the device in portrait
• Slowly tilt the device forward until you're pointing the camera down at the floor. Check the preview image is still orientated correctly
• Check that landscape orientations still work correctly too.

Needs review: @SergioEstevao

[koke]

If you set the phone to landscape, then point it down, the preview will turn to portrait.

I think the underlying problem is that we don't want to look at device orientation, but adjust the preview orientation to the interface orientation: regardless of the actual position of the phone, only show landscape if the UI is landscape.

[koke]

AVCaptureVideoOrientation can't be directly mapped to UIDeviceOrientation, as their values are different.

[frosty]

Thanks @koke, I hadn't thought about landscape using face down orientation too. I've switched things over to use the interface orientation, as you suggested, and I've explicitly mapped to the correct values.

Better?

[SergioEstevao]

Working great @frosty.

[frosty]

Thanks @SergioEstevao and @koke!