WestJet announced that it has introduced an ultra low-cost fare — and if you like carry-ons, seat choice and earning points, there's a catch.The UltraBasic fare will replace the airline's basic fare option, and it comes with "some restrictions," according to an email that was sent to WestJet members.Carry-on bags aren't permitted unless a passenger is on a transatlantic or transpacific flight, or bought the airline's extended comfort option, the email said.Passengers can check a bag in advance f