Enhance TLS configuration (nginx + bind)

[n-peugnet]

Based on these steps but not strictly: https://community.letsencrypt.org/t/howto-a-with-all-100-s-on-ssl-labs-test-using-nginx-mainline-stable/55033

Todo:

• [x] setup CAA in DNS (https://blog.qualys.com/product-tech/2017/03/13/caa-mandated-by-cabrowser-forum)
• [x] remove weak cipher suites (https://security.stackexchange.com/a/207812)
• [x] enable TLS session cache (http://vincent.bernat.im/en/blog/2011-ssl-session-reuse-rfc5077.html)
• [x] setup HSTS for club1.fr
• [x] add club1.fr to chromium HSTS Preload list (https://hstspreload.org/?domain=club1.fr)
• [ ] generate and use strong dhparams (useless with only an ECDSA key and without an RSA key)

[n-peugnet]

Done