allow sorting by weighted sum on official trade

I like to use weighted sums to find the items which will actually most benefit my build. For instance, for amulets, added physical damage to attacks is about equal with crit multiplier, but much much better than crit chance. But crit chance still counts for something! However, right now I can only set the threshold.

Ideally, this would be done the same way that pseudo mods are currently handled, where there's a spot on the displayed item which shows the current value, which I can click on to sort the items by that stat. That would also let me see what the actual weighted sum is for each item. That's useful because, for instance, an amulet with 50 life and a weighted sum score of 250 is worse than one with 80 life and a weighted sum score of 248, but it's annoying to have to incorporate the life into the weighted sum as well as the damage mods. Much easier to just set required life of a certain amount and then look through the 20 or so items which pop out in my price range.

poe.trade does this, and it's one of the major reasons why I still use it.