Bumped version number to 0.9.1
Make StackItem properties public. This is important for plugins that modify the stack, e.g. to point items to a CDN.
Revert "Make StackItem properties public. This is important for plugins that modify the stack, e.g. to point items to a CDN."

This reverts commit a69c9f1e786b12b5fde899992b3e01313b17f776.