[5.4] Move model methods to builder

[themsaid]

This PR moves the create and forceCreate methods to the Builder, this will allow stuff like:

User::on('myCustomConnection')->create();

[dotuancd]

After create new instance, the Model continue call the create() method and create() method is don't exists in Model class. So, it will call to another magic method is __call() and in this method will make query builder instance and call to create() method.