nginxModules.http_proxy_connect_module: init

This adds the nginx module `ngx_http_proxy_connect_module` which allows
to tunnel HTTPS through an nginx proxy[1].

As this module contained patches for several nginx version, some minor
adjustments were needed:

* Allowed each entry in `nginxModules` to provide patches.

* Added an optional `supports` attribute to ensure that each module can
  determine if it supports the currently built nginx version (e.g. stable
  1.14 ATM or mainline 1.15 ATM).

[1] https://github.com/chobits/ngx_http_proxy_connect_module