Import from Taxonomy - Forums

Once the Drupal's default (core) Forum is populated with data, it's impossible to get rid of Taxonomy and use wrapper instead, because import of Forums-Taxonomy data via category_legacy doesn't work correctly. Forum works fine with the wrapper, if starting from scratch (i.e. creating all categories, containers and topics with the wrapper). The problem is, that Forum store data in it's own database-table and variables, including Taxonomy term IDs, which is not updated by category_legacy, and so any existing Forum-data gets broken (Categories are created, but Forum says no containers/categories exists).

I created a patch for category_legacy module, to solve this problem. It searches the Forum's data and corrects the ID's, as well as URL aliases (if changing is enabled), so import of Forums works well, and other imports are not affected,

I also noticed, that the Pathauto module (if enabled) creates duplicate URL aliases on node-creation during import. I don't know if there's something about this in documentation, but I think this should be in help-texts, because this situation is pretty common. It's also included in the patch.

The reverse process (i.e. Category to Taxonomy export of Forums) is not addressed by the patch, sorry (no time to make that). But I think that one-way operation is still much better than nothing, so I marked this as "needs review".