Added a new event for putting items in items frames

Added a new event that is called before an item is displayed in an item frame. You can cancel the event to prevent the item from being placed and used up. Very handy for blocks rendered with TESRs when you just can't make them display properly because of, for example, rotation issues or misplacement issues.

(seems to say something like "fuzz 1" when applying the patch file, but it is tested and it works and nothing is wrong with the code)