Add support for `limit_req_zone` in main nginx config and `limit_req`
for `nginx::resource::location`.

In init.pp
`limit_req_zone` can be a String, or an array of String

In resource/location.pp
`limit_zone` can be a String and should point to a zone defined from
`limit_req_zone` in init.pp

Co-Authored-By: Tim Meusel <tim@bastelfreak.de>

Co-Authored-By: Tim Meusel <tim@bastelfreak.de>