1149265 - Main menu bar appears on top of Favorites menu in IE

- Delete class FavoritesButton, the button was no longer used.
- Create FavoritesMenu,  just the Menu part of the former button class
- Remove various explicit zIndex setting and defer to the css defs in
  play due to the recent work for BZ 1144052.
- Remove the '#' href from the current user dropdown, it navigated
  to nowhere on a click of the button.
- Fix I18N issue in user dropdown. Replace literal "Account Details" with
  "Settings" property. (note, could not add new property for release, so
  chose "Settings" as best existing prop).