Add retry support to row reader.

Takes setting from new parser option.

Uses a new commitOrRetryTransaction method on the transaction service, modeled after what the other store's branch already added. This exposes it to the service directly and implements it for Persistit.

To accomplish the retry, the loader needs to buffer something. I am keeping RowDatas, which seemed the most compact. Users need to be aware that with a very large commit quantum allowing retry will consume a lot of space. If retry is okay, based on the requirements of the active database, just go with a smaller commit quantum.

Depends on an earlier row reader defaults branch, so current diff is a little bigger. Start with 8/21 commits.