Add the ability to do a fake office import using the office viewer

In some cases, when the user doesn't plan to edit the content of the office file after importing it, it is better to just attach the office file and use the office viewer instead of importing the content of the office file like it happens now.

Of course, ideally, when inserting the office viewer macro the user should be able to upload an office file, but since this is harder to implement right now, we can start by adding an option to the office import dialog to perform a fake import using the office viewer.