Add get/set/delete for moving platforms/walls on the physics engine

[FriendlyGecko]

Enhancement request:

Adding properties to get/set/delete moving platforms and walls for the simple platformer physics engine registry just like the ladders list has.

What should be added/changed?

The decorator properties with getters/setters/deleters

What would it help with?

When devs want the option to manipulate the wall/moving platforms registry post init.

[einarf]

Merged 👍