Add new API allowing developers to split the model definition and
configuration into two steps:
1. Build models from JSON config, export them for re-use:
```js
var Customer = loopback.createModelFromConfig({
name: 'Customer',
base: 'User',
properties: {
address: 'string'
}
});
```
2. Attach existing models to a dataSource and a loopback app,
modify certain model aspects like relations:
```js
loopback.configureModel(Customer, {
dataSource: db,
relations: { /* ... */ }
});
```
Rework `app.model` to use `loopback.configureModel` under the hood.
Here is the new usage:
```js
var Customer = require('./models').Customer;
app.model(Customer, {
dataSource: 'db',
relations: { /* ... */ }
});
```
In order to preserve backwards compatibility with loopback 1.x,
`app.model(name, config)` calls both `createModelFromConfig`
and `configureModel`.
f844459311