Added standard menu items to WinForms backend

Signed-off-by: obulat <obulat@gmail.com>

src/winforms/toga_winforms/app.py

@@ -1,5 +1,7 @@
 from .libs import Threading, WinForms
 from .window import Window
+import toga
+import sys
 
 
 class MainWindow(Window):
@@ -17,8 +19,16 @@ def __init__(self, interface):
     def create(self):
         self.native = WinForms.Application
 
-        # Set the menu for the app.
-        # self.native.setMainMenu_(self.menu)
+        self.interface.commands.add(
+            toga.Command(None, 'About ' + self.interface.name, group=toga.Group.HELP),
+
+            toga.Command(None, 'Preferences', group=toga.Group.FILE),
+            # Quit should always be the last item, in a section on it's own
+            toga.Command(lambda s: self.exit(), 'Exit ' + self.interface.name, shortcut='q', group=toga.Group.FILE,
+                         section=sys.maxsize),
+
+            toga.Command(None, 'Visit homepage', group=toga.Group.HELP)
+        )
 
         # Call user code to populate the main window
         self.interface.startup()