Add loadBuiltinModels flag to loopback(options)

When creating an application with a local registry, the default
behaviour is to define only two core models Model & PersistedModel.

The new flag `loadBuiltinModels` modifies this behaviour and instructs
loopback to define all builtin models in the local registry too.

lib/loopback.js

@@ -99,6 +99,9 @@ function createApplication(options) {
   if (loopback.localRegistry || options && options.localRegistry === true) {
     // setup the app registry
     var registry = app.registry = new Registry();
+    if (options && options.loadBuiltinModels === true) {
+      require('./builtin-models')(registry);
+    }
   } else {
     app.registry = loopback.registry;
   }

test/loopback.test.js

@@ -115,6 +115,24 @@ describe('loopback', function() {
     });
   });
 
+  describe('loopback(options)', function() {
+    it('supports localRegistry:true', function() {
+      var app = loopback({ localRegistry: true });
+      expect(app.registry).to.not.equal(loopback.registry);
+    });
+
+    it('does not load builtin models into the local registry', function() {
+      var app = loopback({ localRegistry: true });
+      expect(app.registry.findModel('User')).to.equal(undefined);
+    });
+
+    it('supports loadBuiltinModels:true', function() {
+      var app = loopback({ localRegistry: true, loadBuiltinModels: true });
+      expect(app.registry.findModel('User'))
+        .to.have.property('modelName', 'User');
+    });
+  });
+
   describe('loopback.createDataSource(options)', function() {
     it('Create a data source with a connector.', function() {
       var dataSource = loopback.createDataSource({