Had to disable php-cs-fixer phpdoc rules since it would try to add invalid typehints.

All three supported database engines will return `null` PHP value for a `NULL` value in database.
Previously all ensured values would be cast to the expected type (except for `DateTime` which had a special case for `NULL`), possibly replacing `NULL` value with 0 or other incorrect value.
Let’s make the `null` part of the “type system” using binary or.
It will also be useful once we start adding return type hints for daos methods.

----

```php
$c = $dice->create(helpers\DatabaseConnection::class);
$v = $c->exec('select NULL as "null", 42 as "int", 3.14 as "decimal", CURRENT_TIMESTAMP as "timestamp", \'test\' as "string", true as "true", false as "false";');
var_dump($v);
```

## PHP 8.2
### SQLite
```php
array(1) {
  [0]=>
  array(7) {
    ["null"]=>
    NULL
    ["int"]=>
    int(42)
    ["decimal"]=>
    float(3.14)
    ["timestamp"]=>
    string(19) "2023-02-08 23:07:00"
    ["string"]=>
    string(4) "test"
    ["true"]=>
    int(1)
    ["false"]=>
    int(0)
  }
}
```

### MariaDB 10.6.11
```php
array(1) {
  [0]=>
  array(7) {
    ["null"]=>
    NULL
    ["int"]=>
    int(42)
    ["decimal"]=>
    string(4) "3.14"
    ["timestamp"]=>
    string(19) "2023-02-09 00:06:47"
    ["string"]=>
    string(4) "test"
    ["true"]=>
    int(1)
    ["false"]=>
    int(0)
  }
}
```

### PostgreSQL 14.6
```php
array(1) {
  [0]=>
  array(7) {
    ["null"]=>
    NULL
    ["int"]=>
    int(42)
    ["decimal"]=>
    string(4) "3.14"
    ["timestamp"]=>
    string(29) "2023-02-08 23:06:57.433412+00"
    ["string"]=>
    string(4) "test"
    ["true"]=>
    bool(true)
    ["false"]=>
    bool(false)
  }
}
```

## PHP 7.2
### SQLite
```php
array(1) {
  [0]=>
  array(7) {
    ["null"]=>
    NULL
    ["int"]=>
    string(2) "42"
    ["decimal"]=>
    string(4) "3.14"
    ["timestamp"]=>
    string(19) "2023-02-08 23:23:54"
    ["string"]=>
    string(4) "test"
    ["true"]=>
    string(1) "1"
    ["false"]=>
    string(1) "0"
  }
}
```

### MariaDB 10.6.11
```php
array(1) {
  [0]=>
  array(7) {
    ["null"]=>
    NULL
    ["int"]=>
    string(2) "42"
    ["decimal"]=>
    string(4) "3.14"
    ["timestamp"]=>
    string(19) "2023-02-09 00:24:33"
    ["string"]=>
    string(4) "test"
    ["true"]=>
    string(1) "1"
    ["false"]=>
    string(1) "0"
  }
}
```

### PostgreSQL 14.6
```php
array(1) {
  [0]=>
  array(7) {
    ["null"]=>
    NULL
    ["int"]=>
    int(42)
    ["decimal"]=>
    string(4) "3.14"
    ["timestamp"]=>
    string(29) "2023-02-08 23:24:30.032842+00"
    ["string"]=>
    string(4) "test"
    ["true"]=>
    bool(true)
    ["false"]=>
    bool(false)
  }
}
```

It is not needed since PHP 7.0.

Up to level 5.

Will still require more work on filling in array item types.