Add support for Leaseweb (http://developer.leaseweb.com). This is based on dns_cloudns and I cannot really take credit for it.
I have tested it and it works. I have the following notes:
-Sometimes Leaseweb gives back no response while I would expect an errorMessages (so i now check for empty response or errorMessage).
-the acme.sh _Post() function does not return base64decoded response when base64 is used. Not a real big problem.
-I'm not sure if any other dnsapi provides this functionality. But with this implementation two simultaneous running processes for the same domain will not work (2 TXT files for _acme-challenge at the same time).
