Update YAXAttributes.cs

Added new attribute, called YAXDeserializeInto.

This attribute is used when you want to deserialize an xml type into a certain type, for example, we have issues when deserialize into IEnumerable.

 [YAXDeserializeInto(typeof(List<ParameterGroup>))]
  public IEnumerable<ParameterGroup> ParameterGroups { get; set; }