Navbar 4 - add CSS

multimenu navbar - hover/javascript "togglehc", with added CSS

Adding CSS may not only beautify the navbar, but also makes it more user-friendly:

• Remove list item decorations
• Hide checkboxes
• Links as blocks, so the entire menu item area becomes clickable
• Resize "+" sign to be big enough to click/touch on any screen
• Hover menu item color to easier see which item is selected
• Add border to make margins/paddings visible
• Added "design" style

HTML changes:

• Embed navbars in <nav> tags
• Use two separate links, "Parent" (go to link) and "▶" (expand submenu).
  This separation would not be necessary if dealing only with the click behaviour of a mouse, as the submenu is displayed on hover, before clicking.
  Anyhow, on touch screens, the submenu is displayed in the very moment when touching the link, not before.
  In that case, the links have to been separated, so the touch screen user may choose between either going to the "parent" link or displaying the submenu.
• Swapped "Plus" and "Parent" elements, so the fixed-width "Plus" element comes before the fluid "Parent" elementin the HTML code, even if the "Plus" element visually appears after the "Parent".