[TIMOB-17670] DocumentViewer not displaying PDF files

Details: https://jira.appcelerator.org/browse/TIMOB-17670
When trying to change url in a document viewer instance, it sometimes doesn't load the respective document in url.
Reason is because we are using UIDocumentInteractionController, which according to Apple API documents, is supposed to be a preview controller, and recommended to initialize an instance for every different file previewed.
Bug solved by creating new instance every time url is changed for document view.
I you're going to release and nil the controller, you can remove the entire "if" block and just call `RELEASE_TO_NIL()` at the beginning of the function