Update exhibit

public/admin.html

@@ -125,6 +125,7 @@
       <div class="spacer"></div>
       <span id="dirty" title="unsaved changes"></span>
       <button id="reloadBtn" title="Discard changes and reload from server">Reload</button>
+      <button id="printAnchorsBtn" title="Open printable anchor markers">Print anchors</button>
       <button id="exportBtn" title="Download scene.json">Export</button>
       <button id="saveBtn" class="primary" disabled>Save to server</button>
     </div>