move UIWindow to lua

modules/core_widgets/uiwindow.lua

@@ -0,0 +1,17 @@
+UIWindow = extends(UIWidget)
+
+function UIWindow.create()
+  local window = UIWindow.internalCreate()
+  window:setTextAlign(AlignTopCenter)
+  return window
+end
+
+function UIWindow:onKeyPress(keyCode, keyText, keyboardModifiers)
+  if keyboardModifiers == KeyboardNoModifier then
+    if keyCode == KeyReturn or keyCode == KeyEnter then
+      signalcall(self.onEnter, self)
+    elseif keyCode == KeyEscape then
+      signalcall(self.onEscape, self)
+    end
+  end
+end