Script to generate Let's Encrypt certs and add them to ISPConfig via API

1. The script currently only works with an ISPC installation that has MySQL and Apache.
2. Currently no real SSL Certs can be created. Beta testing ends mid-november and then it should be publicly available so you can use this to test to process and that you can get ssl certs when it's publicly made available.
3. I haven't done all return checks etc. --> expect bugs

1. Get Let's Encrypt - follow instructions here: https://letsencrypt.readthedocs.org/en/latest/using.html
2. Get the le2ispc script (just single script or clone whole repository)
3. Make the le2ispc script executable
4. Optionally: You can copy it to a directory in $$PATH, e.g. /usr/bin
5. In ISPC add a remote user that can at least access the "Site Domain Functions"
6. Edit the header section of the le2ispc script - it's important to give a valid email address
7. Run at least once the letsencrypt-auto script with the auth parameter: cd letsencrypt; ./letsencrypt-auto auth

If you have put the script into a location in $PATH then just type: le2ispc domain.tld.

If not, then go to the place where you have the le2ispc script and run: ./le2ispc domain.tld.

You can optionally append any number of subdomains to be used as alternate names in your certificate, e.g.: le2ispc domain.tld sub1.domain.tld sub2.domain.tld.

To avoid running into a rate limit ("There were too many requests of a given type :: Error creating new cert :: Too many certificates already issued for domain.tld"), you can execute a dry-run with the -n or --dry-run option: le2ispc -n domain.tld sub1.domain.tld sub2.domain.tld. This will only print the letsencrypt command without executing it.