Fix --target overwrite --target-map
#44

Doesn"t check any for locked domains (with .lock file in cache dir).
- same part as for .cer, .key files.

Add flag --dns-servers - for set own servers.

Add cloudflare server 1.1.1.1 for default dns servers.

Sometimes websites has unconditional redirect from http to https or it has problem to handle .well-known/acme-challenge/ requests and redirect it to http-01 validations handler.

For this scenarious it has two additional mechanism:

1. Handle http-01 validation in https reverse proxy
2. Respose with self signed certificate if can"t retrieve normal certificate - it allow ok first http-01 validation by self https reverse proxy, without special handle .well-known/acme-challenge for http version of website.

It was problem is some dns was blocked and doesn"t answer something.
In previous release it waited for full request cert time, instead of few seconds.

Fix small errors and typos from linters.

Fix bug in self check domains:
subdomain www was allowed if it has local record, but have no external dns record. It was couse of error to create certificates.