AUL tables refactoring

Currently for each combination of user + operation + nid we store separate record in DB in three tables: aul, aul_user, aul_node.
We can have only one table "aul":

To create realm name we need:
realm = {op}_{key}_{key_id}

Query for function aul_node_grants($account, $op):

SELECT gid
FROM aul
WHERE key = 'uid', op = $op, amount > 0, key_id = $uid

Query for function aul_node_access_records($node):

SELECT *
FROM aul
WHERE nid = $nid, amount > 0
 
       $grants[] = array(
         'realm' => {op}_{key}_{key_id},
         'gid' => 2,
         'grant_view' => 'value',
         'grant_update' => 0,
         'grant_delete' => 0,
       );