Closes #3157 ## Changes: - The action callback of Trigger now returns the entity that triggered it. - General cleanup of Trigger class - `target` is now 100% separate from `filter`, because that's what the functionality described in the documentation implied (to me). - Converted all the different "default value fallbacks" to a single setup. - Trigger used `Entity` and `Actor` interchangeably. Rewrote it to be 100% Entity (Although Entity doesn't have any collision mechanics build in, so an argument could be made to go for 100% Actor)