table relationship automation 

as i propose in this [issue](https://github.com/paulocaldeira17/angular-websql/issues/7)
I added  'model' as follow:

#### you can inject model:
```js
    var instance = $webSql.openDatabase("name", '1.0', 'Test DB', 2 * 1024 * 1024);
    instance.addModel("articleLight", "article", [{
        table : "comments",
        insertName : "comments",
        foreignKey : "article_id",
        primaryKey : "id",
    }],[{
        table : "user",
        insertName : "owner",
        foreignKey : "user_id",
        primaryKey : "id",
    }]);
```

#### query they them
```js
instance
    .selectModel("articleLight", {title : "Amazin title"})
     .then(function(article){
	    console.log(article.comments.length),
            console.log(article.owner.name),
      })
```