fixes#4856fixes#458fixes#4529fixes#3299
Added API method Block::getSupportType(Facing) : SupportType
Added SupportType enum
fixes torch, lantern, door etc. placement on slabs and upside-down stairs
I wonder if there's a way to generalise item consuming beyond just eating/drinking. Stuff like lava bucket in a furnace needs the same kind of "leftover" logic.
Now, blocks do not respond to silk touch unless specifically opted into. Since this always involves custom drops in one way or another, it's easy enough to figure out which blocks need to be marked for silk touch - anything that overrides getDrops, getDropsForCompatibleTool or getSilkTouchDrops is a block which _might_ need to be flagged. Using these criteria to reduce the number of blocks needing to be checked, I was able to manually invert the behaviour as needed.
This fixes reoccurring bugs with blocks erroneously dropping themselves whenever new blocks are added and someone forgot to set that flag, granting players access to internal blocks with strange behaviour.
