Reply rss is too demanding and time-sensetive

[umputun]

Implementation of #125 and #145 works as designed however practically it makes very "dynamic" rss feed. Such feed provides new items only for some relatively short window (currently 24h). Practically it means we have to have some rss reader/client running at least once a day to pick up all the updates. I'm going to change the logic and keep replies in the feed limited by the number of items only.

Another problem - in order to retrieve replies we pull last comments (up to 1000) and this limit can be way too low for deep history or active sites. Unfortunately, the store doesn't provide any better and more effective way to discover chains/parents. I'll see what can be done here, probably this info can be collected as a part of notification logic, but still not very clear how to deal with all of this.

[umputun]

I have increased limit and window and it should do for the regular activity, but still problematic for heavy sites.