title: Remove File with UIDocumentPickerViewController
body: <p>i want to delete a pdf file (for example a pdf file
  that are present on my iPhone) with the UIDocumentPickerViewController controller. In the info.plist I already support iTunes file sharing and support opening documents...</p>
  
  <p>I want to delete the pdf file in the didPickDocumentsAt urls: method. But It doesn't work. Copy the pdf file into the app bundle is successfully but I can't delete the file from the device.</p>
  
  <p>File should move from the device into my app bundle and delete it in the 
  on my iPhone storage.</p>
  
  <p>I hope you can enlighten me. Thank you.  </p>