Configuration clean up

* Hocon Parser now returns a `HoconRoot` , (`HoconValue` and a list of `HoconSubstitution`)

## Breaking change!

`new ActorSystem("name")` now calls `ConfigurationFactory.Load()` which in turn gets the config from App/Web.config
Earlier versions only used Pigeion.config if no config was supplied.
This change aligns more to Akka.