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/platform.js

@@ -17,9 +17,9 @@ var apps = require('./apps.js'),
     infra = require('./infra_version.js'),
     locker = require('./locker.js'),
     mail = require('./mail.js'),
-    nginx = require('./nginx.js'),
     os = require('os'),
     paths = require('./paths.js'),
+    reverseProxy = require('./reverseproxy.js'),
     safe = require('safetydance'),
     semver = require('semver'),
     shell = require('./shell.js'),
@@ -265,7 +265,7 @@ function startApps(existingInfra, callback) {
         apps.restoreInstalledApps(callback);
     } else {
         debug('startApps: reconfiguring installed apps');
-        nginx.removeAppConfigs(); // should we change the cert location, nginx will not start
+        reverseProxy.removeAppConfigs(); // should we change the cert location, nginx will not start
         apps.configureInstalledApps(callback);
     }
 }