解决ofxml不能正确加载中文的问题, 因为of内部也需要用ofxSonovoUtil的转换方法，所以就直接放到了ofUtil里.并且函数名字由ofx变成了of.
Merge branch 'master' of github.com:yty/openFrameworks into sonovo-master
Merge branch 'sonovo-master' of github.com:yty/openFrameworks into sonovo-master