added ONLY_EXPOSED env parameter

[crunchtime-ali]

Rancher users need to be able to disable dockergens --only-exposed parameter to be able to have their containers detected. We have been using this approach for a year now issuing certificates for 25+ webservices.

The code is originally from @mcnilz (mcnilz@72b1799)

[buchdag]

@dj-hedgehog turns out we did not really need -only-exposed at all, so I believe #230 takes care of this ?

[crunchtime-ali]

@buchdag I just deleted a certificate from one of my domains, started again with the latest docker-letsencrypt-nginx-proxy-companion and started nginx-proxy again but it did not renew the certificate.

I restarted again with my own version from this PR and it renewed the certificate in question.
So I still need it :)

Is there any other information I can provide?

[buchdag]

Right, #230 removed the -only-exposed from /app/start.sh but not from the reload_nginx() function on /app/functions.sh.

I think you can modify the PR to just remove the -only-exposedfrom line 101 on /app/function.sh.

-only-exposed does not appear to be of any use anymore in the case of nginx-proxy + the le companion (as the two templates fed to docker-gen already filter containers through other means), so we probably won't need a feature to turn it back on.

[crunchtime-ali]

I removed all usages of ONLY_EXPOSED I added and removed -only-exposed from /app/function.sh and /app/start.sh

[buchdag]

You are still committing two extra blank lines to README.md (lines 170 & 171 on your branch), remove them and we are good to go.

[crunchtime-ali]

Oops, I missed those. They are gone now.

[buchdag]

LGTM