Trade Window Improvements

[daniu -TLG-]

For the "Offer Trade" window:
- initially show the Trade Partner's items. I know mine, I want to see if he has what I need.
- remember the filters for both the My Inventory and Trade Partner tab individually. It takes a while to set the filter for several games I want and then have to do it over when switching to the other tab.
- in My Inventory, show an indication if an item is already part of a pending trade of yours. I may have lost track and there may be equivalent items.
- in Trade Partner tab, show an indication for items I have already; it's hard to keep each card for each game in mind and as it is now, I have to switch windows all the time to look up badge progress.

Also, it's hard to see why I can't start a trade from a user's profile if that user has a thread open in a trading forum; it's possible from there and I have to find it, or he has to post that trade URL which no one does. It happened often to me that a trade was rejected and I couldn't offer another one because I had closed the user's thread and couldn't find it again. There should be a toggle in the profile to enable it.

And it would be good if you could post a comment along with a trade offer, would make counteroffers much easier.