TSDB: reverse iterator

[valkuc]

Hello. First of all thanks for great project! I'm using it to store events (or log). I want to show last 100 events. In order to achieve that it's necessary to have reverse iterator - to iterate from newest record to oldest. It is possible to implement such iterator?

[armink]

This is a good suggestion. I think the main work is to add the implementation of get_prev_tsl_addr and get_prev_sector_addr for reverse iterator.

[MikeTuev]

Please take a look https://github.com/armink/FlashDB/pull/145