[INPROGRESS] First version of tokumx converter

This pull request aims to add tokumx support to mongoriver by converting tokumx oplog records to mongo oplog records.

cc @ebroder 
Yeah, so this is the big difference between mongo and toku for tailer queries. With toku, you do an `{_id: {$gte: gtid}}` query instead of querying on timestamp. I suspect this is going to have to be refactored a bit more to support that.