In a summer of high-profile restaurant openings, the handlers of Urbana — the new restaurant inside the new Hotel Palomar just west of Dupont Circle on P Street — don’t want their charge to get lost in the crowd. And so, last night, they hosted a flashy preview of their eatery to get the word out about the restaurant that replaces the old Gabriel restaurant in the former Radisson-Barceló. Hotel Palomar is a link in…