Support quick item transfer

When I want to buy all arrows a merchant has I do shift-click and every arrow goes straight to my inventory. When I want to sell only one mushroom I do control-click and it goes into the merchants inventory. Lets call the inventory container for a moment.

It would be nice if any containers (plants, chests, stealing-NPC) would work like that. ATM I only get all/one items "on" my mouse pointer, if I want to put the item(s) into the target container I have to move the mouse there and click to drop it. That's inconsistent and cumbersome. :(

(RM-2522 from redmine: created on 2015-05-08 by Who Knows, )