signal to the webapp once partial reindex is done

[vladak]

Once the configuration listener protocol is extended so that allows more than just Configuration object to be passed, the protocol should be further extended so that partial reindex notifies the webapp to call maybeRefresh() on specific SearcherManager objects. This is a follow-up to the changes for #1132.

[tarzanek]

@tulinkry I think you have this ready with your messaging addition to listener, no ?

[tulinkry]

Yes. Not ready but on the way

[vladak]

Also, with this change it would be good to relax the IndexRefreshPeriod which is currently set to 1 minute so every minute the webapp tries to reopen the indexes which causes syscall and I/O churn.