Add User-Agent header (fixes #453)

Applied ACMEv2 - thanks to darovic!!!

substitute for $domain in default .cfg file

looks for a default .cfg file in "$WORKING_DIR/getssl_default.cfg"

Update getssl

Allow dns checks to deal with CNAME records

Some environments might delegate dns validation to a subzone by using CNAME records. These changes allow getssl to validate dns updates when the verification name is a CNAME to the TXT record rather than a TXT record itself.

Case insensitive processing of agreement url because of HTTP/2

Fixes #425

Spelling

Pipe the commands to nsupdate

Use HTTP 1.1 as workaround atm

Co-authored-by: Robert Eden <rmeden@yahoo.com>

Fixes #423

[Route53] Make a stricter comparison for matching against zone names

This adds a dot in front of the fqdn and the zone name, so the
comparison will only check against full DNS parts of the fqdn and the
zone name. This will prevent to match a fqdn against an unrelated zone
name which overlaps with the wanted zone in the naming.

Fixes #398