Add timestamps and hostname to notification messages

For easier "post-mortem" debugging, the timestamps of the last time the app has responded to an http request resp. has last received updates from the flashlist is added into the message. Also to make it easier to disambiguate from where the message is sent, the hostname is now included in the message.

This should make it easier to see what is happening and also make it possible to spot if it is just a problem with one host (e.g. dead tunnel), or if it is a genuine problem.