Support parent key name as well as parent key id

[bmclean]

We currently support the parent_key_id attribute as an integer id. We should add support for also using a parent key string name. Something like id_or_name.

Example:

def build_model(entity)
  model_entity = new
  model_entity.id = entity.key.id unless entity.key.id.nil?
  model_entity.id = entity.key.name unless entity.key.name.nil?
  if entity.key.parent.present?
    model_entity.parent_key_id = entity.key.parent.id if entity.key.parent.id.present?
    model_entity.parent_key_id = entity.key.parent.name if entity.key.parent.name.present?
  end
  model_entity
end