Allow app.id to be set

lib/models/application.js

@@ -100,7 +100,7 @@ var Application = loopback.createModel('Application', ApplicationSchema);
 Application.beforeCreate = function (next) {
     var app = this;
     app.created = app.modified = new Date();
-    app.id = generateKey('id', 'sha1');
+    app.id = app.id || generateKey('id', 'sha1');
     app.clientKey = generateKey('client');
     app.javaScriptKey = generateKey('javaScript');
     app.restApiKey = generateKey('restApi');