reconsider the Action dynamic dispatch

[kellpossible]

Consider using https://crates.io/crates/enum_dispatch instead of dynamic dispatch, or if I decide to value the ability to have users of this crate be able to implement their own Actions for the system, then figure out a way to remove the ActionType enum and replace it with something else, perhaps an integer order priority method for the Action trait.

[kellpossible]

Or users can make their own Action type if they want custom types. Make api generic over action type.