Trac importer fix:
* error when trying to convert too long ticket ids (closes #719)
Enhancements (#619):
* Trac guide wiki pages skipped
* wiki attachments migration added
git-svn-id:
http://redmine.rubyforge.org/svn/trunk@1175 e93f8b46-1217-0410-a6f0-8f06a7374b81