Fixed mistake in documentation addImage doesn't support gif format
Fix for missing field in particle file.
Merge commit 'refs/pull/4846/head' of git://github.com/cocos2d/cocos2d-x into iss3597-particle-plist
closed #3597: Uses !xxx.empty() instead of xxx.size() > 0.
Merge pull request #4991 from dumganhar/iss3597-particle-plist

closed #3597:  Merge PR #4846