Change certain parts to not require ground

[drifting turtle]

Parts to affect:

• Springs
• Bumpers
• Conveyers
  - Signs of all types (except wall signs)
  When placed, these parts should not create ground beneath them, and should not fall when above void in play mode (the same way that noteblocks work)

Notably, this would remove the possibility of signs and bumpers falling due to being pushed off a ledge by a conveyer, but I think this is a worthy tradeoff -- they can already appear/disappear based on conditions, and are not pushable by the player, so I doubt any puzzles would be affected. This change could be versioned if I'm wrong about that.

[silver hollow]

I use the fact that I can push signs on a conveyor into a pit for minigame score counters/timers

[drifting turtle]

Signs I'm totally willing to compromise on, since they can be placed on invisible moving platforms to achieve a similar effect, just thought it would be convenient if nobody is actually using that behaviour. Conveyers and springs are the more important parts of this post

[silver hollow]

I agree about conveyors yeah

springs too I think?

springs can be placed on platforms now and weirdly they won't fall if the platform moves away, unless it's on water

which is super funny in Emberstone and Dewdrop because their moving platforms are exactly the shape of springs. you can't even see a platform under a spring until/unless it moves out from under it