feat: Improve construction element handling

This change implements several additional construction methods,
  including the first polygon ones. In particular, it now allows
  arbitrary strings as entity names, even ones that are not allowed
  as GeoGebra identifiers, using captions to show the original
  entity names. In addition, line arguments are interpreted as a pair
  of point arguments as needed.

  Resolves #6.
  Resolves #30.
  Resolves #31.

public/index.html

@@ -8,6 +8,7 @@
     <h2>Joyce Geometry Applet</h2>
     <ul>
       <li> <a href="inscribed-equilateral.html">Before</a> </li>
+      <li> <a href="inscribed-revived.html">Revived</a> </li>
       <li> <a href="inscribed-modified.html">After</a> </li>
     </ul>
     <h2>WRL Files</h2>