title: Xamarin forms button with no border issue
body: <p>I try to render a list of clickable items in a view. I would like to add a button with an image and a white border (the first one). I discovered that the buttons in my StackLayout/ViewCell can't render a border.</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;ContentPage 
  xmlns="http://xamarin.com/schemas/2014/forms" 
  xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" 
  xmlns:controls="clr-namespace:XLabs.Forms.Controls;assembly=XLabs.Forms"
  x:Class="*.PlacesPage"
  Title="TEST"&gt;
  &lt;ContentPage.Padding&gt;
      &lt;OnPlatform x:TypeArguments="Thickness" iOS="0, 20, 0, 0" /&gt;
  &lt;/ContentPage.Padding&gt;
  &lt;ContentPage.Content&gt;
      &lt;Grid&gt;
          &lt;ListView x:Name="lvPlaces" ItemsSource="{Binding Places}" SeparatorColor="Gray" SeparatorVisibility="Default" RowHeight="120" &gt;
              &lt;ListView.ItemTemplate&gt;
                &lt;DataTemplate&gt;
                    &lt;ViewCell&gt;
                      &lt;ViewCell.View&gt;
                          &lt;StackLayout Orientation="Horizontal"&gt;
                              &lt;Button HorizontalOptions="Center" VerticalOptions="Center" BorderWidth="3" BorderColor="White" Text="IMG"&gt;&lt;/Button&gt;
                              &lt;Button Text="{Binding Name}" BorderWidth="0" FontSize="20" BackgroundColor="Transparent" Clicked="OnButtonClickedPlace"&gt;&lt;/Button&gt;
                          &lt;/StackLayout&gt;
                      &lt;/ViewCell.View&gt;
                    &lt;/ViewCell&gt;
                &lt;/DataTemplate&gt;
              &lt;/ListView.ItemTemplate&gt;
          &lt;/ListView&gt;
      &lt;/Grid&gt;
  &lt;/ContentPage.Content&gt;
  </code></pre>
  
  <p></p>