Cumulated activity time is negative. about m8m

[MaxDZ8]

Note: this was designed broken (on purpose). I was undecided on whatever this should be a client or miner feature so I hacked it in as fast as possible.

I later realized that while having the monitor do something useful is nice, it involves keeping the ports open for no real benefit. Plus: this takes very little and it's really useful to monitor mining activity long term.

Next version will feature internal management of those events and will log them to some external file (likely .csv).