Power statistics in Joules at lifetime tab

[DBotThePony]

Currently, at lifetime tab of power network statistics we get an average Watts usage over lifetime of that power network, which make no sense for me (and im pretty sure for others). My suggestion is: to make lifetime power network statistic show energy usage in joules, so we can get information which machines consume the most energy. Other tabs should be untouched, because average watts over 1h/10h/50h/... make sense.