Improve vBulletin importer

- FEATURE: TopicCreator now supports 'pinned_at' parameter
- FIX: 🐛 FIX TopicQuerySQL to support pinned topic older than 2010
- FIX: 🐛 Properly remove all HTML Entities from Usernames/Titles/Category Names/Groups in vBulletin importer
- FIX: 🐛 Properly handle specific vBulletin BBCode (quotes/mentions)
- FIX: 🐛 Make sure we generate a username from the name of the user instead of a fake email
- FEATURE: Allow for custom timezone in vBulletin importer
- FEATURE: Support for profile pictures/background in vBulletin importer
- FIX: 🐛 merge the categories tree to only 2 levels in vBulletin importer

script/import_scripts/base.rb

@@ -229,7 +229,7 @@ class ImportScripts::Base
     results.each do |result|
       u = yield(result)
 
-      # block returns nil to skip a post
+      # block returns nil to skip a user
       if u.nil?
         users_skipped += 1
       else