Config control command

[kehiy]

trafficstars

We can make a command set that helps you create, change, and manage config file, as well as set a password and encrypt the config file with the password. If a user has a password, we can ask for the password, otherwise we use config normally.

If you think it's a good idea, please assign this issue to me to work on this feature.

[kehiy]

@mattn Can you kindly check this? I believe we can make this client much better...

[mattn]

Sounds good to me, please do.

[kehiy]

@mattn Thanks, I'll start working on that. You can assign it to me as well. I'll make a PR once it finished.