RESTAdapter : Convert errors object returned with a 422 in an Ember Object
Use App.Model.total to store the total number of elements given in the meta data of the request
Store the total number of elements given in the meta data of each request into `App.modelCount`
RESTAdapter : When a record become invalid, all the embedded records become invalid too
REST Adapter : When a record become valid, all the invalid records in the request which failed become valid too
Errors set on embedded object is an Ember Object