Thing Browser Control: fixed cosmetic focusing issue. When Things list is...

Thing Browser Control: fixed cosmetic focusing issue. When Things list is focused, you can now start typing to change the Filter.
Edit Action window: Actions list is now automatically focused on mouse over. When Actions list is focused, you can now start typing to change the Filter.
Edit Effect window: Effects list is now automatically focused on mouse over. When Effects list is focused, you can now start typing to change the Filter.
Game Configurations: added "Gold Wand" to all ZDoom-based Heretic configurations (also a couple of cosmetic tweaks).
Game Configurations: changed "Pistol" display sprite to the one provided with (G)ZDoom.