cck 6.x-2.0-rc10

- Advanced help modules were omitted from the previous release, they are added in here.
- Get rid of helper function content_is_updated(), we can do it better using the content version variable.
- #318224 by brmassa, fix several errors in Content Copy.
- #318387 Make sure old fieldgroup updates don't run if tables were never created.
- #318227 Clean up update abort logic to more clearly explain what still needs to be done, add a helper function to prevent dangerous database operations until database is updated.
- #317232 Change css file name from content.css to content-module.css to avoid namespace collisions.
- #316656 Default weight must be zero, not NULL, or form ordering will be incorrect.
- #107407 by dopry, optimization patch, do nothing in hook_form_alter() and hook_nodeapi() if there are no fields.
- #317932 Fix userreference documentation typo.