The shell is embedded in the node and offers the ability to monitor
and control the node via the launching terminal.
Still to do:
* Switch to a fork of CRaSH that we can maintain ourselves, and merge in Marek's SSH patch so we can enable SSH access.
* Add persistent command history that survives restarts.
* Tab completion for the 'flow' and 'run' commands.
* Remove the 'jul' command and replace it with a command that lets you see and tail the log4j logs instead.
* Fix or remove the other crash commands that have bitrotted since 2015.
