DolphinWX: Break up ConfigMain.cpp into separate classes

Prior to this, ConfigMain.cpp was a large (52KB) cpp file that contained all of the UI setting code.

This breaks up the config code into subclasses of wxPanel, which are then just instantiated to add to the settings wxNoteBook. This keeps all the settings categories separated from one another and also cleans up the code in general.

Source/Core/DolphinWX/Config/GameCubeConfigPane.h

@@ -0,0 +1,43 @@
+// Copyright 2015 Dolphin Emulator Project
+// Licensed under GPLv2
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <wx/arrstr.h>
+#include <wx/panel.h>
+
+class wxButton;
+class wxCommandEvent;
+class wxCheckBox;
+class wxChoice;
+class wxString;
+
+class GameCubeConfigPane final : public wxPanel
+{
+public:
+	GameCubeConfigPane(wxWindow* parent, wxWindowID id);
+
+private:
+	void InitializeGUI();
+	void LoadGUIValues();
+	void RefreshGUI();
+
+	void OnSystemLanguageChange(wxCommandEvent&);
+	void OnSkipBiosCheckBoxChanged(wxCommandEvent&);
+	void OnSlotAChanged(wxCommandEvent&);
+	void OnSlotBChanged(wxCommandEvent&);
+	void OnSP1Changed(wxCommandEvent&);
+	void OnSlotAButtonClick(wxCommandEvent&);
+	void OnSlotBButtonClick(wxCommandEvent&);
+
+	void ChooseEXIDevice(const wxString& device_name, int device_id);
+	void ChooseSlotPath(bool is_slot_a, TEXIDevices device_type);
+
+	wxArrayString m_ipl_language_strings;
+
+	wxChoice* m_system_lang_choice;
+	wxCheckBox* m_skip_bios_checkbox;
+	wxChoice* m_exi_devices[3];
+	wxButton* m_memcard_path[2];
+};