Create folders in Bagger when creating a new bag

[matthewpburgess]

It would be useful to have the ability to create folders in both the payload and tag files when creating a new bag.

For example, I would like to create a 'metadata' folder in the tag files before adding files to that folder.

Example bag structure:

• base directory/
  • bagit.txt
  • manifest-md5.txt
  • bag-info.txt
  • data/
    • [payload files]
  • metadata/
    • [tag files]