Loose check for all int types in Model::is_changed()

Actual code works well when `data_type` is `int`, but does not take into account `tinyint` or `mediumint` or `int unsigned`.

The `type` key from the `$properties` always contain `int` in all this situations.

If this is the correct change, we should also change the doc, which doesn't include the `type` key in the examples.