Lucene.Net.Search.ReferenceContext<T>: Converted to ref struct and reworked TestControlledRealTimeReopenThread.TestStraightForwardDemonstration() to verify functionality

Lucene.Net.Search.ReferenceContext<T>: Converted to ref struct and reworked TestControlledRealTimeReopenThread.TestStraightForwardDemonstration() to verify functionality #372