changed counters findandmodify to upsert
Merge pull request #256 from tyronegroves/counters_upsert

Changed Counters FindAndModify to upsert so that the collection is created on the first checkpoint
Fix typo
Failing test for correct bucket in OptimisticEventStream tests. Remove usage of Bucket.Default in OptimisticEventStream ctor.
Use bucketid when creating CommitAttempt in optimistic event stream.
Using long instead of int for checkpoint numbers in sql and mongo storage.
When wiring up Mongo persistence, can supply a delegate to return a connection string (in conjunction with the exisitng connectionName). (Cherrypicked from v4 branch)