六世紀中国七尊仏にみえる螺髻像について:『維摩経』の螺髻梵王とその図像=On the Buddhist Images with Rahotsu(snail-like curls of hair) Seen among the Set of Seven Sacred Deities(Principal Image and Six Attendants) in the Sixth Century China: Description of Bramā with Rahotsu in Vimalakīrti Sutra and the Painted Images