message: Style checkboxes correctly
diff: <Border Grid.Row="2" Grid.ColumnSpan="3" Background="LightGray" Opacity="0.5" Padding="12" Margin="0.12" />
  - <CheckBox x:Name="AcceptTermsCheckbox" Grid.Row="2" Grid.ColumnSpan="2" HorizontalAlignment="Left" Margin="12,12,48,12">
  + <CheckBox x:Name="AcceptTermsCheckbox" Style="{StaticResource MahApps.Styles.CheckBox.Win10}" Grid.Row="2" Grid.ColumnSpan="2" HorizontalAlignment="Left" Margin="12,12,48,12">
  <TextBlock
  TextWrapping="Wrap"
  Foreground="{DynamicResource MahApps.Brushes.ThemeForeground}">
  <HierarchicalDataTemplate DataType="viewmodels:TreeItem" ItemsSource="{Binding VisibleMeasures}">
  <StackPanel Orientation="Horizontal">
  - <CheckBox VerticalAlignment="Center" IsThreeState="{Binding IsThreeState}" IsChecked="{Binding IsSelected, Mode=TwoWay}" />
  + <CheckBox Style="{StaticResource MahApps.Styles.CheckBox.Win10}" VerticalAlignment="Center" IsThreeState="{Binding IsThreeState}" IsChecked="{Binding IsSelected, Mode=TwoWay}" />
  <TextBlock Text="{Binding Name}" />
  </StackPanel>
  </HierarchicalDataTemplate>
  </TreeView.ItemTemplate>
  </TreeView>
  - <StackPanel Grid.Row="2" Orientation="Horizontal">
  - <TextBlock Text="{Binding SelectionTreeData.SelectedTreeItemCount}" />
  - <TextBlock>&#x202F; Selected</TextBlock>
  + <StackPanel Grid.Row="2" Margin="0,12" Orientation="Horizontal">
  + <TextBlock Text="{Binding SelectionTreeData.SelectedTreeItemCount}" FontWeight="Bold" />
  + <TextBlock FontWeight="Bold">&#x202F; Selected</TextBlock>
  </StackPanel>
  </Grid>
  <TextBox Grid.Column="1" Grid.Row="1" FontFamily="Courier New" FontSize="16" VerticalScrollBarVisibility="Visible"
  