Customize/Normalize class-level remoting http path

Some ways to specify the handling of the http path generation:

``` javascript
// Path setting
var User = ds.define('UserAccount', {name: String, bio: String}, { path: 'accounts' }); // setting
console.log(User.http.path); // result: '/accounts'

// Relation path setting - final api: /accounts/1/public-photos
User.hasMany('Photo', { 
  as: 'publicPhotos', 
  scope: { where: { public: true } }, 
  options: { path: 'public-photos' }
});

// Normalization (global)
ModelBuilder.prototype.normalizePathName = true; // ex: through dataSource at runtime

// Normalization (per-model)
var User = ds.define('UserAccount', {name: String, bio: String}, { normalize: true }); // setting
console.log(User.http.path); // result: /user-accounts

// Override the normalization method (default: dasherized lowercase)
ModelBuilder.normalizePathName = function(pathName, className, properties, settings, parent) {
  return 'data/' + pathName; 
};

```
I suggest that we put the `path` property under `http`, for example:
```
http: {
   path: '/my-models'
} 
```
This will be consistent with other mappings, such as:
```
mongodb: {
  collection: 'my-collection'
}
```