add challenge mirror, verify, format functionality

[MilyMilo]

Adds ctf challenge mirror <challenge> and ctf challenge verify <challenge> adapted from #106

Originally, this functionality was called pull and verify - however, push is already used to push challenge changes to the git repository. I think mirror is a better name, as ctfcli will attempt to mirror / copy the remote state from ctfd. This way pull stays in its current git-like form, for git-related operations.

More additions:

• I've removed update / create / verify files - this can be achieved by just using --ignore=files.
• I've added files_directory_name (defaulting to dist) to specify where ctfcli should download the files, relative to challenge.yml
• I've added a warning when there are additional challenges on the remote, that are not registered locally
• ctf challenge verify will exit with status code 2 if the verification was successful, but some challenges are out of sync.
• I've fixed some typos

Thanks to @reteps for the initial contribution!

Closes: #101 #106

[MilyMilo]

Also I think we'll want to add mirror after performing the deploy, so that we can get the updated connection_info, or even simply update the local challenge with connection_info, and use the new implemented challenge.save() method.

[reteps]

Hi there,

I no longer have time to land this PR, but I have some additional changes on my fork you may want to port over after a lot of testing with my college club. Good luck landing this!

[ColdHeat]

I like the choice of subcommands here. mirror and verify make sense.

In terms of the deploy I think if we can mirror just the connection_info it would be best.

[ColdHeat]

@MilyMilo This seems good to go. Is this still WIP or ready to merge?

[MilyMilo]

Yeah let's add the mirror after sync, I'll do that now.

[MilyMilo]

Okay so some more changes:

• connection_info will be added to the challenge.yml after deployment
• I've added a challenge format command to enforce the formatting used by ctfcli. It's pretty simple but running mirror will output challenge.yml files in that format, so if we want to be consistent we might as well format everything the same way.
• I've added the new commands to the README