ui/ux: set min windows size and change hamburger button size

Change-Id: Iecaf466faac615b54458a268c98c8457d4c62750
Tuleap: #790

App.xaml.cpp

@@ -63,6 +63,7 @@ App::OnLaunched(LaunchActivatedEventArgs^ e)
         Window::Current->Content = rootFrame;
     }
 
+    ApplicationView::GetForCurrentView()->SetPreferredMinSize(Size(500, 500));
     Windows::UI::ViewManagement::ApplicationView::PreferredLaunchViewSize = Size(800, 700);
     Windows::UI::ViewManagement::ApplicationView::PreferredLaunchWindowingMode
         = Windows::UI::ViewManagement::ApplicationViewWindowingMode::PreferredLaunchViewSize;

MainPage.xaml

@@ -114,7 +114,7 @@
                                 <Button x:Name="_toggleSmartBoxButton_"
                                         Grid.Row="0"
                                         FontWeight="Bold"
-                                        FontSize="30"
+                                        FontSize="26"
                                         Content="&#xE700;"
                                         Click="_toggleSmartBoxButton__Click"
                                         FontFamily="Segoe MDL2 Assets"