[feature/avatars] Rework UCP to be simpler/more consistent

Redesigning the UCP avatar page to use javascript to make use less
confusing. This design is also more easily transfered to the ACP for
group avatars, which will give better consistency in the long run.

PHPBB3-10018

phpBB/includes/avatar/driver/remote.php

@@ -72,6 +72,8 @@ class phpbb_avatar_driver_remote extends phpbb_avatar_driver
 			$url = 'http://' . $url;
 		}
 
+		require_once($this->phpbb_root_path . 'includes/functions_user.' . $this->phpEx);
+
 		$error = array_merge($error, validate_data(array(
 			'url' => $url,
 		), array(