savefile corruption screen and escort RTB waypoints

ui/corruptedsavemenu.py

@@ -0,0 +1,17 @@
+from tkinter import *
+from tkinter.ttk import *
+
+from ui.window import *
+
+
+class CorruptedSaveMenu(Menu):
+    def __init__(self, window: Window):
+        super(CorruptedSaveMenu, self).__init__(window, None, None)
+        self.frame = window.right_pane
+
+    def display(self):
+        self.window.clear_right_pane()
+
+        Label(text="Your save game was corrupted!").grid(row=0, column=0)
+        Label(text="Please restore it by replacing \"liberation_save\" file with \"liberation_save_tmp\" to restore last saved copy.").grid(row=1, column=0)
+        Label(text="You can find those files under user DCS directory.").grid(row=2, column=0)