including extension method overloads to take an Expression tree for predicates.
CR Changes
refactored object to BsonDocument conversion.
added expression sort support to the fluent aggregation and find interfaces.
added expression helper for unwind.
CR Changes
CSHARP-1093: Introduced IChannel in order to allow ClusterableServer to intercept NotMasterExceptions.
CSHARP-1093: Replace the ExecuteProtocolAsync methods in IChannel with 7 more specific methods (delete, getMore, etc...).