AFK Notification & Merchant Interface Improvement

Hi,

those small fixes should help a lot:
- if a player is /afk, another player who whispers to that player should be notified (eg. "This player is currently away")
- remember bag selection in the merchant interface: selections which items from which bag are displayed should be saved. Eg. for me I have all stuff for sale in the backpack and if only this bag is displayed, I can't accidently (because of a game lag/ brain damage) sell something from the belt pouch.

About your first point, you can just press N and set yourself to away, busy, or offline, and then people will be notified when they try to whisper to you. It's even easier than going /afk since you can do it without actually being afk.

OK, this should then definitly merged.