Fixes #1247

Adds a new user default with key SEQUENCER_NODE_SORT_ORDER_REVERSE,
which defaults to NO (meaning the sequencer nodes sort the original way)

To change the sort order, either launch the app via Terminal:

    SpriteBuilder -SEQUENCER_NODE_SORT_ORDER_REVERSE YES

OR to change the sort order permanently

defaults write SpriteBuilder SEQUENCER_NODE_SORT_ORDER_REVERSE YES