Adding doc-comments to CacheBehaviour.
BREAKING CHANGE to FastCacheBehaviour.

Looks like the previous use of ReferenceEquals wasn't always working. I was getting null errors when trying to use this in my game. So in the effort of fastest speed with little safety, I've gone a new route to remove properties from FastCacheBehaviour entirely! Instead they're just plain fields which makes them even faster to access, but now you either have to call the Reset*Cache method for the specific component you want, the ResetCache() method to get all the components, or ResetCacheDestroyed() to get all components that are no longer valid. Or you can manually assign them now that they're just plain fields.

This will break existing usages but makes the class even more performant and simplified.