allow inner margin helper to inherit down
allow inner margin helper to inherit down

ButchersBoy/MaterialDesignInXamlToolkit,tipunch74/MaterialDesignInXamlToolkit,tipunch74/MaterialDesignInXamlToolkit,ButchersBoy/MaterialDesignInXamlToolkit,ButchersBoy/MaterialDesignInXamlToolkit,DingpingZhang/MaterialDesignInXamlToolkit,tipunch74/MaterialDesignInXamlToolkit