add applyScale system

[AlexBezuska]

Example:
any entity with:

"scale": {
  "current": 0.5
}

will be scaled to 50% of it's original size.

The scale only happens if the scale has changed since last frame, and is the "current" scale persent is below the "max".

To set a max:

"scale": {
  "current": 0.5,
  "max": 1
}

This system creates or changes a "last" property each time it successfully scales an entity, this prevents scaling every frame by comparing the "last" with "current" and only scaling if they differ.