PHPStan was complaining in 'plugins/auth_internal/init.php' due to UserHelper::hash_password() being passed a string, rather than a UserHelper::HASH_ALGO_* constant.  Just switching the param to string for now.

Also some formatting for readability.

Also update 'select_hash' and 'select_tag' values param, which can have int or string keys.

fix HOOK_QUERY_HEADLINES being invoked with different argument lists, add some more phpdoc comments for base plugin class

 * arguably better hack for incompatible plugins causing E_COMPILE_ERROR