shorten all commands names down to ~4 characters

* In tork(1):
  * the `o` input command character is now named `b`

* In tork-driver(1):
  * the `run_all_test_files` command is now named `test!`
  * the `over` message is now named `boot!`

* In tork-engine(1):
  * the `reabsorb_overhead` command is now named `boot!`
  * the `run_test_file` command is now named `test`
  * the `run_test_files` command is now named `test`
  * the `stop_running_test_files` command is now named `stop`
  * the `rerun_passed_test_files` command is now named `pass!`
  * the `rerun_failed_test_files` command is now named `fail!`
  * the `list_failed_test_files` command is now named `fail?`
  * the `over` status message is now named `boot!`
engine: add `test?` and `pass?` listing commands