Landscape support

[ralfebert]

It would be nice if there would be support for setting the view to landscape orientation.
Maybe just treating them as a separate Device? Like:

extension Device {
  public var size: CGSize {
    switch self {
    // ...
    case .iPadAir: return CGSize(width: 768, height: 1024)
    case .iPadAir_Landscape: return CGSize(width: 1024, height: 768)
    // ...
  }
}

[skyweb07]

I'm thinking about opening the Device size extension to allow passing custom size so we don't need to rely on the defined properties so it's more extensible