make the config path configurable

lib/load-config.js

@@ -1,11 +1,14 @@
+/* jslint node: true */
+"use strict";
 var config;
+var configPath = process.env.CRYPTPAD_CONFIG || "../config/config";
 try {
-    config = require("../config/config");
+    config = require(configPath);
     if (config.adminEmail === 'i.did.not.read.my.config@cryptpad.fr') {
         console.log("You can configure the administrator email (adminEmail) in your config/config.js file");
     }
 } catch (e) {
-    console.log("You can customize the configuration by copying config/config.example.js to config/config.js");
+    console.log("Config not found, loading the example config. You can customize the configuration by copying config/config.example.js to " + configPath);
     config = require("../config/config.example");
 }
 module.exports = config;