Add configuration warning to Box2DWorld/PhysicsBody nodes that have a non-identity global transform scale

[briansemrau]

Following discussion here: #8 (comment)_

There is no reasonable way to support scale transformations for Box2DPhysicsBody, Box2DFixture, or Box2DWorld nodes. These nodes should display a warning if their global relative-to-box2dworld scale is not (1, 1) to indicate that physics will behave in unexpected ways.

[jordo]

I think Box2DWorld would still work, if Box2DPhysicsBody transforms end up being relative to world instead of global? If i 'zoom in' and scale the Box2DWorld node, it shouldn't affect any transforms if transforms end up being relative to world