JERUSALEM-Prime Minister Menahem Begin said Monday that Israel is providing training, supplies and artilery support to Christian militiamen in south Lebanon. It is Israel's duty"to prevent what he called an attempt at "genocide" by Palestinian forces in Lebanon. Begin blasted France for failing to intervene on behalf of Christian villagers and soldiers who have been under earch all Issues siege in south Lebanon for months. He said that "Christian France, the patron of the Maronite Christians for ages. had sold them down the river" to carry favor with the Arab oil-producing countries who support the Palestinians. IT HAS BEEN known...