Rename Block -> Node

[SoniEx2]

Anything that refers to a Block should refer to a Node, anything that refers to a BlockFactory should refer to a NodeFactory.

Block implies type, while node implies position and associated data (including type), so "node" is more correct than "block".

(In a perfect world we'd have "Node" and "Block" but "Block" has ambiguities which are solved by calling it "NodeFactory")

[RX14]

IRC log (edited) for reference: https://aww.moe/14lssq.txt