(First Part of a Two-Part Series)   By LARRY ANTHONY PANNELL     Whether it is your first visit to the jungle-shrouded Buddhist citadel or a return trek to re-witness the wonders of its timeless palatial opulence, you cannot help but be engulfed by an overriding sense of calm and tranquility when you arrive at Angkor Wat. The pervasive ataraxia of its impeccably