entity_property_verify_data_type() should not enforce an absolute URI

For the uri data type entity_property_verify_data_type calls valid_uri() with the absolute parameter set to TRUE. This seems overly restrictive as a valid URI does not have to contain a scheme.

This also prevents saving what would be considered a valid URI value for the link field through the entity_metadata_wrapper, ex:

This will succeed:

$node = node_load(123);
$wrapper = entity_metadata_wrapper('node', $node);
$wrapper->field_link->url->set('http://test.com');
$wrapper->save();

While this will fail:

$node = node_load(123);
$wrapper = entity_metadata_wrapper('node', $node);
$wrapper->field_link->url->set('test.com');
$wrapper->save();