Abstract properties are not Serialized and Deserialized and serialization got stuck in other case if remove IgnoreIndex attribute from abstract class

[Waqas-Zamir]

Below is the sample abstract and concrete class.

[ZeroFormattable]
public abstract class BaseAggregate
{
    public abstract string AggregateId { get; set; }
}

[ZeroFormattable]
public class AccountAggregate : BaseAggregate
{
    // ZeroFormatter requires virtual keyword with each property to be serialized
    // But a member marked as override cannot have virtual keyword
   [Index(0)]
   public override string AggregateId { get; set; }
}

The ZeroFormatter.ZeroFormatterSerializer.Serialize<AccountAggregate>(accountAggregateObject) got stuck.

And if I put IgnoreIndex attribute on AggregateId property in base class. The serialize and deserialize works but the deserialized object doesn't contain value in the AggregateId property.

[nsentinel]

@Waqas-Zamir You can use a source with my changes (#76) to overcome this issue.