merge certificates.js and nginx.js to reverseproxy.js

when certs change, we have to call into nginx anyway. since they
go hand in hand, just merge those files. modern reverse proxies
do this job integrated already.

src/cron.js

@@ -10,7 +10,6 @@ var apps = require('./apps.js'),
     assert = require('assert'),
     backups = require('./backups.js'),
     caas = require('./caas.js'),
-    certificates = require('./certificates.js'),
     cloudron = require('./cloudron.js'),
     config = require('./config.js'),
     constants = require('./constants.js'),
@@ -20,6 +19,7 @@ var apps = require('./apps.js'),
     dyndns = require('./dyndns.js'),
     eventlog = require('./eventlog.js'),
     janitor = require('./janitor.js'),
+    reverseProxy = require('./reverseproxy.js'),
     scheduler = require('./scheduler.js'),
     settings = require('./settings.js'),
     semver = require('semver'),
@@ -175,7 +175,7 @@ function recreateJobs(tz) {
     if (gJobs.certificateRenew) gJobs.certificateRenew.stop();
     gJobs.certificateRenew = new CronJob({
         cronTime: '00 00 */12 * * *', // every 12 hours
-        onTick: certificates.renewAll.bind(null, AUDIT_SOURCE, NOOP_CALLBACK),
+        onTick: reverseProxy.renewAll.bind(null, AUDIT_SOURCE, NOOP_CALLBACK),
         start: true,
         timeZone: tz
     });