Update Orm\Model::to_object() to allow same parameters as to_array()

I just ran across this case that did not support getting custom properties within a stdClass-object when running ```to_object()``` on an Orm\Model.

This fix introduces the same arguments ```to_object($custom = false, $recurse = false)``` as there are for ```to_array()```. This allows for getting custom properties into the stdClass object representation of an Orm-object.