title: How to make Cocoa document package type with it's extension hidden by default?
body: <p>I'm making a Cocoa application which uses document package (bundle) as it's data.
  I specified an extension and Finder now recognizes the folder with the extension as a document well.
  But the folder's extension is still displaying, and I want to hide it by default (like application bundle) Is there an option to do this?</p>