KABUL, Afghanistan — By plane, motorbike, camper van and even on bicycles, tourists are beginning to discover Afghanistan , with solo travelers and tour groups gradually venturing into a country that until recently was wracked by war. And the country’s Taliban government, which seized power more than three years ago but has yet to be formally recognized by any other nation, is more than happy to welcome them. “The Afghan people are warm and welcoming and wish to host tourists from other