Deserialization works wrong with class which has inherited serializable properties

When using RFAttributedDecoder to deserialize, inherited attributed property is nil, even though it has appropriate serialization key.

Start at RFAttributedDecoder and trace how attributed properties and their serialization keys are collected during deserialization, paying attention to inherited properties. Reproduce the case with a class that inherits a serializable attributed property and verify that the property is populated rather than nil.

Written by the indexing model from the issue text.