If the user begins editing an empty file which corresponds to a file in the /etc/examples directory offer to load this example for editing. Suggested by Tom Smyth.

Otherwise pfctl -e will never be run during boot, leaving pf disabled by default.

add 'show environment', 'setenv', and 'unsetenv' commands

Being able to manage environment variables from within nsh will be useful, especially if nsh is used as a login shell because nsh's environment is visible to other commands run by nsh. Setting variables can now affect the behaviour of nsh itself. For example, it is possible to set NSH_MANUAL_PAGE from within a running nsh session and the new value will immediately be used by the 'manual' command. This particular variable is only useful to nsh developers themselves but the same mechanism could be used for user-facing variables in the future. If 'show environment' is run without further arguments all variables will be displayed. Otherwise the value of the specified variable will be displayed if the variable exists. All commands support tab-completion for names which already exist in the environment. The 'setenv' commands appends "=" if the name being completed does not yet exist in the environment.

add crontab commands: show crontab, crontab edit, crontab install

ok stsp@

ok stsp@

For now, display and edit the crontab file of the root user only. The "show crontab" command displays the root user's crontab as shown by the crontab -l command. Editing is implemented via a new CTL handler which knows about the semantics of the crontab(1) command. If an NSH configuration contains crontab rules then the "crontab install" command appears in the running-config in order to install the crontab file managed by nsh to the system with crontab(1).