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
this implementation is very rough due to having to hack around lots more MCPE bullshit, and currently doesn't allow dynamic coral types; but it's there. We'll clean this up after 1.13 migration is done.