Allow mojits to extend YUI modules in other mojits

This pull request allows mojits to easily extend YUI modules of other mojits. For example:

mojits/Vehicle/controller.server.js

```js
YUI.add('VehicleController', function (Y, NAME) {
    var Vehicle = function () {
        this.type = 'Vehicle';
        this.transmission = 'automatic';
    };

    Y.namespace('mojito.controllers')[NAME] = Vehicle;
    Y.extend(Vehicle, Y.Base, {
        index: function () {
            ac.done(ac.params.body('brand') + ' ' + this.getType());
        },
        getType: function () {
            return this.type;
        }
    });
}, '0.0.1', {
    requires: {
        'oop',
        'mojito-params-addon'
    }
});
```

mojits/Motorcycle/controller.server.js

```js
YUI.add('MotorcycleController', function (Y, NAME) {
    var Vehicle = Y.mojito.controllers.VehicleController,
        Motorcycle = function () {
            Motorcycle.superclass.constructor.call(this);
            this.type = 'Motorcycle';
            this.transmission = 'manual';
        };

    Y.namespace('mojito.controllers')[NAME] = Motorcycle;
    Y.mojito.util.extend(Motorcycle, Vehicle);
}, '0.0.1', {
    requires: {
        'mojito-util',
        'VehicleController'
    }
});
```

In this example, the Motorcycle mojit extends the Vehicle mojit, which extends the Y.Base class (extending Y.Base is not a requirement, the example just illustrates multiple level of extensions). Notice that the controllers can be defined as a function; this allows mojits to extend using Y.extend, which ensures that the prototype chain is maintained regardless of how many levels of extensions. Also notice that the Motorcycle controller does not have to re-specify the 'mojito-params-addon' requirement; it just has to specify the Vehicle controller requirement, and its addon will automatically include any addon required by Vehicle controller.

To ensure that mojit dependencies work with resourceStore > lazyMojits on, mojits depending on other mojits should specify their dependencies in defaults.json:

mojits/Motorcycle/defaults.json
```js
[{
    "settings": [ "master" ],
    "dependencies": [ "Vehicle" ]
}]
```
When there is a tunnel request and mojits/langs are loaded lazily, then the loader meta data on the client becomes out of date and so here we update the loader on the server and add the loader to meta.assets such that the client loads the new loader meta.