SimulatorActions is no longer an enum. It is an extendable singleton. It allows you to extend the action space but it is quite strict about it. Actions cannot be put on different ints, actions cannot be remove.
There is now a registry for action space configurations.

Our registry pattern is far from idea and thus we haven't used it consistent. This PR aims to resolve this by copying the registry pattern used in Pythia (as it is much nicer) and then registering all current measures and sensors and using the register to query for those instead of getattr as this is a more clearly extendable pattern (as compared to monkey patching).