Entities: Add version property to entities upon creation.

[digisomni]

Summary

In the interest of allowing entities to be properly handled and upgraded, without assumptions, every entity is assigned a semantic version upon its creation. This is a read-only property to the scripting API and can only be changed by copying properties to a new entity.

[ctrlaltdavid]

How does this property differ from the UUID? That also is a read-only unique identifier.
How is it envisaged that the version property be used?

[digisomni]

Entity JSONs have a single version at the top if I recall correctly, this instead moves that version number into each entity. The UUID is to identify the entity, the version is to determine what set of "properties" it has and can legally have so we can perform fix-up, determine compatibility, etc.

[stale]

Hello! Is this still an issue?

[stale]

Hello! Is this still an issue?