Cluster + instance improvements

-Moved the database initialize call out of the instance code into the prestart script so that it is now only called once when you start the explorer even if you are running multiple cpus/threads
-The database connection function now uses the default connection string in the event a connection string is not supplied
-Removed unused reference to lib/explorer.js code from the cluster file

bin/instance

@@ -6,30 +6,21 @@ var app = require('../app');
 
 app.set('port', process.env.PORT || settings.webserver.port);
 
-var dbString = 'mongodb://' + encodeURIComponent(settings.dbsettings.user);
-dbString = dbString + ':' + encodeURIComponent(settings.dbsettings.password);
-dbString = dbString + '@' + settings.dbsettings.address;
-dbString = dbString + ':' + settings.dbsettings.port;
-dbString = dbString + '/' + settings.dbsettings.database;
+db.connect(null, function() {
+  var server = app.listen(app.get('port'), '::', function() {
+    debug('Express server listening on port ' + server.address().port);
+  });
 
-db.connect(dbString, function() {
-  // initialize the database
-  db.initialize_data_startup(function() {
-    var server = app.listen(app.get('port'), '::', function() {
-      debug('Express server listening on port ' + server.address().port);
-    });
+  process.on('SIGINT', () => {
+    server.close(() => {
+      var mongoose = require('mongoose');
 
-    process.on('SIGINT', () => {
-      server.close(() => {
-        var mongoose = require('mongoose');
-
-        mongoose.connection.close(false).then(() => {
-          // close the main process now that all http and database connections have closed
-          process.exit(0);
-        }).catch((err) => {
-          console.log(err);
-          process.exit(1);
-        });
+      mongoose.connection.close(false).then(() => {
+        // close the main process now that all http and database connections have closed
+        process.exit(0);
+      }).catch((err) => {
+        console.log(err);
+        process.exit(1);
       });
     });
   });