(GH-3681) Add explicit WindowCommand styles for Button/ToggleButton
(GH-3681) Add explicit WindowCommand styles for Button/ToggleButton

- Add new style `MahApps.Styles.Button.WindowCommands`
- Add new style `MahApps.Styles.ToggleButton.WindowCommands`

batzen/MahApps.Metro,MahApps/MahApps.Metro,ye4241/MahApps.Metro