Lots of bug fixes and support for non-gawk versions of awk

2020-01-22 #475 and #483 Fix grep regex for >9 subdomains in json_get 2020-01-24 Add support for CloudDNS 2020-01-24 allow file transfer using WebDAV over HTTPS 2020-01-26 Use urlbase64_decode() instead of base64 -d 2020-01-26 Fix "already verified" error for ACMEv2 2020-01-29 Check awk new enough to support json_awk 2020-02-05 Fix epoch_date for busybox 2020-02-06 Bugfixes for json_awk and nslookup to support old awk versions (2.17)