CSHARP-915: added MaxWriteBatchSize to IsMasterResult
CSHARP-915: added MaxWireBatchSize to server info.
CSHARP-915: changed MongoServerInstance.MaxWireBatchSize to MaxBatchCount.  Using MongoServerInstance.MaxBatchCount in MongoCollection.
corrected issue with not setting MaxBatchCount in all cases. Also added MongoDefaults.MaxBatchCount.
CSHARP-797: Throw an exception if a bulk operation is empty or Execute is called more than once.