Added Drag and Drop stacking in Inventory, Just drag same item on another and they will stack.
Stack volume is only shown on stack-able items now. Added information about stack maximum.
Solved issue with item quality when stacked in hands via stack buttons - should be fully functional now.
Please note that drop and stack, stacking when picked up and stacking with shortcut does not work with item quality yet. This will be done shortly after drag and drop is tested.