Fix _set*UidSet accessors
CategoryTool: clean up getCategoryParentUidList
CategoryTool._setCategoryMemberShip: bugfixes and cleanup

- duplicated default categories were dropped when the list of categories was
  passed without their base categories
- accept any iterable for 'category_list'
CategoryTool: remove ancient _cleanupCategories migration method
CategoryTool.getAcquiredCategoryList: do not duplicate loopback value on categories
CategoryTool: optimize getCategoryList and getAcquiredCategoryList
CategoryTool: remove broken/unused getRelatedValueList parameters
WIP: support for ZODB index of categories
WIP: index 'delivery' categories in ZODB