Creativity - Creative Building in Survival

- Palette swap: click a material in a placement's materials list to build it from another block, oak as spruce or stone bricks as deepslate bricks. The rest of the set follows along (oak stairs, slabs, fences, doors and logs turn spruce too), which you can turn off. Stairs keep their facing, signs their text.
- Blocks already built in the old material are swapped out by the build, and the old blocks go into the Build Chest.
- "As designed" and "Undo all" take a swap back. Only that placement changes; your saved build stays as it is.
- Scaled-up builds are hollow inside their thick walls where nobody can see, so they need fewer blocks.
- Client and server both need 1.2.0.