Improved error messages in ActionsList
Testing eventObject passing with sub actions
Added multiton facility to `PubSub`

`PubSub` class has static method `instance(id)` that will return (and create if needed) unique instance of `PubSub` per `id`
Added multiton facility to `Frontier`

`Frontier ` class has static method `instance(id)` that will return (and create if needed) unique instance of `Frontier ` per `id`
Cleaned up `Frontier`
Frontier API
Updated library exports
Updated library exports
Merge branch 'feature/frontier-api' into develop