Fix: More asynchronous glob operations and graceful-fs.

Hope this fixes the "Error: EMFILE, too many open files" in
NodeInformationRetrievalJob.

See: https://github.com/freifunkhamburg/ffffng/issues/13

server/db/database.js

@@ -1,7 +1,7 @@
 'use strict';
 
 var async = require('async');
-var fs = require('fs');
+var fs = require('graceful-fs');
 var glob = require('glob');
 var path = require('path');