title: Retrieve options already applied to a holoviews object
body: <p>When I apply options to a holoviews object (Element, Layout, Holomap, ...), is it possible to retrieve those options later on?</p>
  
  <pre><code>p=hv.Points(np.random.rand(100,2)).options(width=700, size=10, color='r')
  </code></pre>
  
  <p>Given <code>p</code>, (how) can I find <code>width=700, size=10, color='r'</code>?</p>
  
  <p>I've gone through all the attributes of <code>p</code> and also looked through <code>StoreOptions</code> but to no avail.</p>