Adding option to save and load state by timestamp

Load by timestamp: load last state is expanded from 1 to 8 actions, for newest to oldest state

Save by timestamp: overwrite the oldest state (or use an empty slot if available)

Adding remaining hardcoded state keys to hotkey dialog

Adding a program exit hotkey

Source/Core/DolphinWX/Src/Frame.h

@@ -289,6 +289,7 @@ private:
 	void OnLoadStateFromFile(wxCommandEvent& event);
 	void OnSaveStateToFile(wxCommandEvent& event);
 	void OnLoadLastState(wxCommandEvent& event);
+	void OnSaveFirstState(wxCommandEvent& event);
 	void OnUndoLoadState(wxCommandEvent& event);
 	void OnUndoSaveState(wxCommandEvent& event);