BERN, Switzerland - When Paul Klee applied for Swiss nationality after fleeing Nazi Germany, his request was refused because it was feared that if his art should "take root in Switzerland, it would insult real art and cause good taste to deteriorate." Sixty-six years later, the work of the painter _ now considered one of the greatest modern artists _ has found a permanent home in Bern, the Swiss capital that finally accepted him. The Zentrum Paul Klee, which opens Monday, will house over 4,000 pieces of Klee's creations _ one of the world's largest collections from a single artist....