In order to write an equivalent tutorial for Xamarin, I am first
following the UWP tutorial.
Fixed many little spelling mistakes and rephrased some sentences.
Fixed a crash when video is requested but the device has no camera.
Fixed a crash when opening an audio recording. (Linphone.Content.FilePath
returns a path with mixed '/' and '\'. I don't know why and I'm not sure
I understand why the file was auto-downloaded either)
