title: When should I use FrameworkPropertyMetadata or UIPropertyMetadata over plain PropertyMetadata?
body: <p>When looking at sample attached properties and behaviors, I've seen a mishmash of uses of <code>FrameworkPropertyMetadata</code>, <code>UIPropertyMetadata</code> and <code>PropertyMetadata</code>. Since they all form an inheritance hierarchy, how do I choose which one to use?</p>