mod_lua: add Dbh:query_rows

mod_lua: add Dbh:query_rows

The added method, query_rows, allows the retrieval of rows from a database without the need for a callback function, it fetches the rows and returns 3 arguments as show below.

```lua
local success, rows, err = dbh:query_rows(sql)
```

This function performs better with large number of rows. Test results below 50k rows returned.

dbh:query(sql, callback) - 0.335949 seconds
dbh:query_rows(sql) - 0.253178 seconds