Added context menu to canvas

PixiEditor/Views/MainWindow.xaml

@@ -183,6 +183,16 @@
             </ItemsControl>
         </StackPanel>
         <Grid Grid.Column="1" Grid.Row="2" Background="#303030">
+            <Grid.ContextMenu>
+                <ContextMenu>
+                    <MenuItem Header="_Select All" Command="{Binding SelectionSubViewModel.SelectAllCommand}" InputGestureText="Ctrl+A" />
+                    <MenuItem Header="_Deselect" Command="{Binding SelectionSubViewModel.DeselectCommand}" InputGestureText="Ctrl+D" />
+                    <Separator/>
+                    <MenuItem Header="_Cut" Command="{Binding ClipboardSubViewModel.CutCommand}" InputGestureText="Ctrl+X" />
+                    <MenuItem Header="_Copy" Command="{Binding ClipboardSubViewModel.CopyCommand}" InputGestureText="Ctrl+C" />
+                    <MenuItem Header="_Paste" Command="{Binding ClipboardSubViewModel.PasteCommand}" InputGestureText="Ctrl+V" />
+                </ContextMenu>
+            </Grid.ContextMenu>
             <Grid>
                 <DockingManager ActiveContent="{Binding BitmapManager.ActiveDocument, Mode=TwoWay}" 
                                            DocumentsSource="{Binding BitmapManager.Documents}">