Added Scythe tool - mows down grass/crops/leaves

Will search in a 5x5x5 (configurable) area for any BlockFlower or leaves
(only one type per use) and harvest them
Has a black/quasi-whitelist - by default, pumpkin/melon stems are
completely ignored, while crops will only be harvested if they are at
the maximum growth stage.
Other crops can be added to the whitelist, even other blocks that are
NOT instances of BlockFlower or are leaves...

Iron only for now, also texture needs work...