Defines the possible states of the ProAct.Actor instances.
A closed ProAct object.
For example Streams that can emmit events anymore are closed streams.
Properties which value can not be updated are closed (constants).
Ended it's lifecycle.
Every ProAct.Actor can be
destroyed. All the resources it uses are freed.
All the dependent objects don't depend on it anymore.
For example if an application has states/routing, Actors that were active in one
of the states should be
destroyed before going into other route/state.
Error has occured in the ProAct.Actor's lifecycle.
For example, if there was an exception in the object's initialization.
Initialized : It is not usable yet.
For example a computed property (property depending on other properties/actors) is
init state when it's created and not read yet.
When something reads its value it computes it for the the first time and becomes in