Added 2 new command's for Nginx that mimic Apache2's a2ensite and a2dissite command

See https://blog.kamal.io/post/nginx-apache-like-server-structure/ for more info.
Merge pull request #22 from Ilyes512/add_new_commands

Added 2 new command's for Nginx that mimic Apache2's a2ensite and a2dissite command