fixed broken test when running tests against a replica set.
Prototype operations.
Moved WriteConcern processing from SendMessage in MongoConnection to WriteGetLastErrorMessage and ReadWriteConcernResult in the WriteOperation base class.
Replaced MongoCursorEnumerator with ReadOperation.
Added CommandOperation.
Removed RunCommandAs from MongoConnection and replaced it with a Create method on CommandOperation which simplifies creating low level commands.
Alternate approach to getting rid of RunCommandAs method from MongoConnection by instead letting each of the (only) three classes that called it have their own helper methods. The helper methods are private and could potentially evolve independently.
Added abstract ReadOperation to hold WrapQuery method. Consolidated WriteConcern handling in SendMessageWithWriteConcern.
Removed throwOnError parameter from Execute method of CommandOperation.