Rework models to use the new 2.0 layout

Split model definition and model configuration.

 - `models/` is a require()-able component providing all shared models.

 - `html5/models` is another require()-able component providing
   html5-specific models like LocalTodo.

 - `api/models.json` and `html5/models.json` contain data-source
   configuration for the loopback apps.

Modify package.json to track github branch 2.0
of both loopback and loopback-boot.
Refactor out `lbclient/` from `html5/`

Move all loopback-related code out of `html5/app.html5.js`
into a new component `lbclient/`.
Refactor `window.connected()` to a service

Modify the `client/` to provide a `network` API with a single
property: `isConnected`.