desc: category mod/ed referenced by id
  table: change moderator moderator_handle varchar(32), + 
      change editor editor_handle varchar(32)
  table: add moderator int(11) unsigned not null, + 
      add editor int(11) unsigned not null
  [loop: (uid, uhandle) select distinct u.id, u.handle + 
      from users u, category c +
      where u.handle = c.moderator_handle or u.handle = c.editor_handle
    pop: update category set moderator = *uid where moderator_handle = *uhandle
    pop: update category set editor = *uid where editor_handle = *uhandle
  ] 
  table: drop moderator_handle, drop editor_handle