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
tork(1): fix crash when typing in `t` without args

lib/tork/cliapp.rb:65:in `test': wrong number of arguments (0 for 2..3) (ArgumentError)
        from lib/tork/cliapp.rb:65:in `recv'
        from lib/tork/server.rb:46:in `block (2 levels) in loop'
        from lib/tork/server.rb:38:in `each'
        from lib/tork/server.rb:38:in `block in loop'
        from lib/tork/server.rb:36:in `catch'
        from lib/tork/server.rb:36:in `loop'
        from lib/tork/cliapp.rb:9:in `loop'
        from bin/tork:128:in `<top (required)>'