Renamed CGuiHandler to GameEngine

- class CGuiHandler is now called GameEngine to better describe its
functionality
- renamed global GH to more clear ENGINE
- GH/ENGINE is now unique_ptr to make construction / deconstruction
order more clear and to allow interface / implementation split
- CGuiHandler.cpp/h is now called GameEngine.cpp/h and located in root
directory of client dir

client/widgets/RadialMenu.cpp

@@ -14,7 +14,7 @@
 #include "TextControls.h"
 
 #include "../eventsSDL/InputHandler.h"
-#include "../gui/CGuiHandler.h"
+#include "../GameEngine.h"
 #include "../gui/WindowHandler.h"
 #include "../render/IImage.h"
 #include "../CGameInfo.h"
@@ -120,15 +120,15 @@ void RadialMenu::gesturePanning(const Point & initialPosition, const Point & cur
 
 		if (newSelection)
 		{
-			GH.statusbar()->write(newSelection->hoverText);
+			ENGINE->statusbar()->write(newSelection->hoverText);
 			newSelection->setSelected(true);
 		}
 		else
-			GH.statusbar()->clear();
+			ENGINE->statusbar()->clear();
 
 		selectedItem = newSelection;
 
-		GH.windows().totalRedraw();
+		ENGINE->windows().totalRedraw();
 	}
 }
 
@@ -140,10 +140,10 @@ void RadialMenu::gesture(bool on, const Point & initialPosition, const Point & f
 	auto item = findNearestItem(finalPosition);
 
 	// we need to close this window first so if action spawns a new window it won't be closed instead
-	GH.windows().popWindows(1);
+	ENGINE->windows().popWindows(1);
 	if (item)
 	{
-		GH.input().hapticFeedback();
+		ENGINE->input().hapticFeedback();
 		item->callback();
 	}
 }