Add Encoding Supports Hints to ScoreData

[webern]

When Finale writes a MusicXML file, it includes this information:

    <encoding>
      <software>Finale v26.2.2 for Mac</software>
      <encoding-date>2020-06-01</encoding-date>
      <supports attribute="new-system" element="print" type="yes" value="yes"/>
      <supports attribute="new-page" element="print" type="yes" value="yes"/>
      <supports element="accidental" type="yes"/>
      <supports element="beam" type="yes"/>
      <supports element="stem" type="yes"/>
    </encoding>

We should add a function to ScoreData that can infer the supported elements and attributes from the data in our score, and add these encoding hints.