Add permission check when attaching assets, and do not create entry if assets parameter is invalid. bugid:111790
Refactor MT::Entry::update_assets(). bugid:111790
Add permission check when updating assets, and do not update entry if assets parameter is invalid. bugid:111790
Refactor MT::Entry::attach_categories(). bugid:111790
Fix typo. bugid:111790
Refactor MT::Entry::update_categories(). bugid:111790