More bootstrap4 fixes to nav.html
More bootstrap4 fixes to nav.html

According to the bootstrap docs, dropdown items require the
'dropdown-item' class

Likewise, items in the navbar require the 'nav-link' class

The class="caret" requirement is no longer required in bootstrap4

CTPUG/wafer,CTPUG/wafer,CTPUG/wafer,CTPUG/wafer