Default theme implementation for a form element.
Available variables:
attributes: HTML attributes for the containing element.
errors: (optional) Any errors for this form element, may not be set.
prefix: (optional) The form element prefix, may not be set.
suffix: (optional) The form element suffix, may not be set.
required: The required marker, or empty if the associated form element is not required.
type: The type of the element.
name: The name of the element.
label: A rendered label el