New Entities Features

Adds...
* Stretchability, true Dimensions
* Angular Velocity
* Visibility
* registration point - now you can rotate or place entities based on an location within the entity space, this allows for easier editing and rotating
* natural dimensions
* new UI for "natural dimensions"
* fixes the crash in butterflies.js

this fixes an issue in moving entities... the old code attempted to find old and new entities based on the "cube" for the entity, but in cases where that cube straddled the edge of the domain, this check would fail... by checking the clamped cube (actually a box) we get the correct behavior