fixing ReplicaSetConfig Equals method.
CSHARP-1136: Removed SecondaryAcceptableLatency from code and replaced it with LocalThreshold. Added support for localThresholdMS into connection string.
CSHARP-1146: Modify ReadPreference to use Optional<T> and With method.
update console test app to shutdown properly.
CSHARP-1123: removed unnecessary classes after refactoring connection handle to use same pattern as elsewhere in code.