Support int and short in SetEntityIdentities for PostGres

[andtii]

When having a model with the Identity as a Int or Short and returning Ids in Bulkoperations there is an exceptions setting the value is the IdentityResult model because its a long poperty trying to set Int64 to Int32. This fix checks the result type and casts it to the correct type

[Map("test")]
public class TestModel
{
[Primary, Map("id")]
public int Id { get; set; }
}

the model has int defined causing exception on the Bulk Operations returning identity which this fix will solve