Fix a bug with layered properties

Properties can now be within other properties!
Rework the ItemPotion property, fixes #693

I realize half of this is inside the previous commit... git loves
messing with me.
Anyway, potions now work perfectly :D
Properly fire the 'player consumes item' event

Also add a dItem determine option.
Merge pull request #695 from mcmonkey4eva/master

Pull request for fixing broken things