feature request: add a `exercism restart` command

[meleu]

description

Add a command to "revert to exercise start".

Just like in the Web UI:

My first thought is an use like this:

exercism restart --exercise=freelancer-rates --track=javascript

Maybe ask for a confirmation before getting rid of user's files (and --force option to not ask for confirmation).

use case

I downloaded an exercise a few days ago but only worked on it today and submitted my solution.

After that I went to the Web UI and noticed the exercise was updated (the requirements/functions to be implemented were changed).

I wanted to get the default boilerplate to restart the exercise from scratch and wasn't able to get it via CLI.

(fortunately @SleeplessByte showed to me how to do it via web UI ❤️)

[meleu]

I've just noticed that the kind of issue I'm trying to solve in this request is related to these ones:

• #1007
• #802

[pedreviljoen]

@meleu
added support in this PR:
#1032

[asarkar]

+1 for an option to update the exercise without overwriting student solution. @pedreviljoen Is there a way to have your PR looked at? Have you tried tagging any of the maintainers in your PR?

I'm using a shell script to do this, see #1007 (comment)