小海龟画图Algoid

★ fix tail call bug ★ fix events scope bug ★ fix default colors ★ all algoid variables onChanged event! ★ move util.eval to eval (root scope) ★ new function exists to test if variable exists ★ new methods util.toClipboard and util.fromClipboard ★ fix clone parameter evaluation bug ★ ARRAY.containsAll ★ ARRAY.containsAny ★ ARRAY.union ★ ARRAY.intersection ★ ARRAY.complement ★ ARRAY.difference ★ ARRAY.product ★ NUMBER.limit ★ algo.setRGB ★ algo.setBgRGB