Content type structure to be completely updated on import, including fields updates and fields removals

Issue Summary

Content Copy module allows to import a node definition exported from elsewhere. However, if you want import a new version of the same content type, you will only end up with the new fields added (if any). If you dropped or changed any of the pre-existing fields, nothing will happen to them: the destination content type will keep the old fields, even if the new definition does no longer include them.

The patch attached changes this behaviour. The main reason that led me to do this, it to make the process I described in this article working 100%.

I might probably be missing something, but I believe this is the correct behaviour that this procedure should have.

The patch change and add a few lines here and there in the function content_copy_import_form_submit.

Successfully tested on the latest stable release of Drupal.