Support SQL query cache

[c9s]

[c9s]

PreparedQuery $pq = QueryCachePool::cacheBy('cache-key', function(....) use ($name) {

 $q = new SelectQuery;
 $q->select('id');
 $q->where()
      ->equal('name', $name)
 return $q;

});

[c9s]

We might need to apply different data to the query string, thus this issue needs more thinking.