Fixup installation with resolved

Fix a problem when systemd-resolve is not activated. The detection is now well-made.

First release

This version is tested on Fedora 29 and Ubuntu 18.04, that should work on others distributions.

Name resolution may take some time before domain refresh is effective. Do not be afraid to run a "nslookup" command multiple times on the domain name in question to verify that your containers are responding.

• Can be used with systemd-resolved
• Examples are working
• Makefile can take several options, chech the README file

Help is welcome for the future work.