Removed unused PartyMenuPopup.cs.

Fixed issue with multiple target popups. Now when you are attacking or clicking a target, it will make only one window.
Still need to work out a bug in the BattleGUITmp function in Pokemon/PokemonDomesticated.cs, where the window target is reset constantly, so you cannot change targets or close the target window while you are being attacked. I figure that is a minor issue right now though, and I want to commit this before something else changes!