1. Network can be shared between several execution, being used by an Rc-handle.
2. The neighborhood is just network's all peers with removed/inserted hosts delta with respect to network.
3. An AIR script is transformed into a separate value of type `TransformedAirScript`. It allows running several
particles on the same parsed AIR script, sharing state.
4. `TestExecutor` was renamed to `AirScriptExecutor`. It also has a constructor that accepts a `TransformedAirScript`.
