Fixes #136 SMF 2 attachments are calculated wrong

Also fixed issues with duplicated attachment names and duplicated code in smf1
Merge remote-tracking branch 'origin/feature' into feature
Fixes #139 usepostcount defaults to 0

Also added usethreadcounts, showimages and showvideos and fixed a bug with invisible for phpBB 3
Fixes #138 Improve BBCode Parser

This should at least convert all default BBCodes without problems
Prepare 1.8.1 release
Fixes #144 vB4 attachments are unapproved
Fixes #145 vB attachments moduke throws an error with the log
Fixes #148 & #149 SMF Poll votes issues
Fixes #146 Polls are attached to all threads
Fixes #147 WBB polls aren't attached to their threads
Fixes #154 lastactive and lastvisit can be "0"