Added Index for the snapshot and journal collection
Added Index for the snapshot and journal collection

akkadotnet/Akka.Persistence.MongoDB,Silv3rcircl3/Akka.Persistence.MongoDB,Silv3rcircl3/Akka.Persistence.MongoDB,akkadotnet/Akka.Persistence.MongoDB,Aaronontheweb/Akka.Persistence.MongoDB,Aaronontheweb/Akka.Persistence.MongoDB