panel: Reorder, fixes, certbot with --nginx

[Linux123123]

Big reorder, added more dividers, made code simpler to read, changed up the order a bit, remade perform_install, remade OS specific installs, removed redundant apt update, removed unused variables, added --nginx instead of --standalone, removed a lot of redundant checks for OS version (if it checks if OS is the correct and that it is supported against a hard coded list, we don't need to recheck that every time we run something).

	No SSL	ASSUME SSL	SSL
Ubuntu 20.04	✅	✅	✅
Ubuntu 18.04	✅	✅	✅
Debian buster	✅	✅	✅
Debian stretch	✅	✅	✅
CentOS 7 *	✅	✅	✅
CentOS 8 *	✅	✅	✅

Fixes #88

[Linux123123]

@vilhelmprytz A thing to say is that when using --nginx when it fails it doesn't edit any files, so if it fails it just makes the site with no ssl.
Also in this PR you can see that there are no nginx_ssl. This is because option --nginx automatically adds all the needed thing for ssl and converts a no ssl config to ssl config.
So basically there is no way to assume_ssl after using certbot with --nginx, because the files aren't edited if certificates fail. I don't see this as a flaw.

[vilhelmprytz]

@vilhelmprytz A thing to say is that when using --nginx when it fails it doesn't edit any files, so if it fails it just makes the site with no ssl.
Also in this PR you can see that there are no nginx_ssl. This is because option --nginx automatically adds all the needed thing for ssl and converts a no ssl config to ssl config.
So basically there is no way to assume_ssl after using certbot with --nginx, because the files aren't edited if certificates fail. I don't see this as a flaw.

Yes, I see your point. I remember I mentioned I was going to implement certbot --nginx myself separately? This PR is way too big for me to do in one go, you've piled up too much work in one PR. Is it too late to ask if you can split it up in smaller separate PRs?

[Linux123123]

@vilhelmprytz A thing to say is that when using --nginx when it fails it doesn't edit any files, so if it fails it just makes the site with no ssl.
Also in this PR you can see that there are no nginx_ssl. This is because option --nginx automatically adds all the needed thing for ssl and converts a no ssl config to ssl config.
So basically there is no way to assume_ssl after using certbot with --nginx, because the files aren't edited if certificates fail. I don't see this as a flaw.

Yes, I see your point. I remember I mentioned I was going to implement certbot --nginx myself separately? This PR is way too big for me to do in one go, you've piled up too much work in one PR. Is it too late to ask if you can split it up in smaller separate PRs?

A bit late I would say. I have a solution. We can do the review threw discord and quickly go threw all of the stuff that I have done. It would be really hard for me to split this PR.

[vilhelmprytz]

Also sorry for taking so long before properly reviewing your PR. When you move a lot of the functions around in conjunction with all the changes, it makes it harder for me to review in one go. 🙂

I think we're closing in on a merge now. I've got to test the script using Let's Encrypt before merge (after all review change requests are resolved).

[Linux123123]

Ok all OS are tested now.

[vilhelmprytz]

LGTM 👍