message: Scope page up and page down to a particular menu section
diff: // page up: jump five items up, stopping at the top
  // the number 5 is used so that we go one page in the
  // inner-scrolled Dependencies and Versions fields
  - switchTo = currentLink;
  - for (var n = 0; n < 5 && switchTo; ++n) {
  - switchTo = previous(allItems, switchTo);
  + switchTo = currentItem || allItems[0];
  + for (var n = 0; n < 5; ++n) {
  + if (switchTo.previousElementSibling && switchTo.previousElementSibling.className == 'pure-menu-item') {
  + switchTo = switchTo.previousElementSibling;
  }
  - if (!switchTo) {
  - switchTo = allItems[0];
  }
  break;
  case "pagedown":
  // page down: jump five items down, stopping at the bottom
  // the number 5 is used so that we go one page in the
  - // inner-scrolled Depedencies and Versions fields
  - switchTo = currentLink;
  - for (var n = 0; n < 5 && switchTo; ++n) {
  - switchTo = next(allItems, switchTo);
  + // inner-scrolled Dependencies and Versions fields
  + switchTo = currentItem || last(allItems);
  + for (var n = 0; n < 5; ++n) {
  + if (switchTo.nextElementSibling && switchTo.nextElementSibling.className == 'pure-menu-item') {
  + switchTo = switchTo.nextElementSibling;
  }
  - if (!switchTo) {
  - switchTo = last(allItems);
  }
  break;
  }
  