Adding CCDataVisitor and CCPrettyPrinter

The usage of CCPrettyPrinter is:
<pre>
    CCPrettyPrinter vistor;
    CCDictionary* pDict = CCDictionary::createWithContentsOfFile("animations/animations.plist");
    pDict->acceptVisitor(vistor);
    CCLog("%s", vistor.getResult().c_str());
</pre>