R1:7a96de10f07a

Hide seen transactions by default in all modern applications

Summary:
Ref T2222. This restores the "N older comments are hidden." shield to all ApplicationTransactions applications. Roughly the rule this uses is that transactions older than your most recent comment are hidden, under the assumption that you've already read and dealt with them, since you replied afterward. Then we show your last comment to remind/contextualize you, and anything afterward. We also don't hide transactions if we'd only be…