Support for adding dhparams file on apache and nginx

[aalmenar]

Apache 2.4 can have a DHParams file to be faster while using DHE ciphers and so on.

Nginx can use also this file on the ssl_dhparam.

[hrak]

you can use the openssl_dhparam resource from openssl cookbook for this:

Like so:

openssl_dhparam '/etc/nginx/ssl/dhparam.pem' do
  key_length 2048
  generator 2
end