Update letsencrypt command

[Pamplemousse]

Fix #30

• remove domains from main letsencrypt_command
• one command per domain: better granularity and control over which certs exists or not to be generated

[thefinn93]

Let's Encrypt has a pretty low ratelimit on certs per second level domain. For this reason, I would rather allow and encourage SANs instead of individual certificates

[auzias]

@thefinn93 a few days after your comments, letsencrypt updated its rate limits (up to 20 Certificates per Registered Domain per week).

I guess then that this fork could be considered to be pulled (once the conflict are resolved). I happen to encounter the same need, due to the same usage restriction.

[thefinn93]

I would consider merging this regardless of the Let's Encrypt ratelimit as long as it's opt-in. Like, just have a boolean that enables it.

[rfleschenberg]

+1 for making it opt-in, I'm concerned it could break existing setups.

[thefinn93]

Closing this for now, feel free to re-open when it's opt-in.