[OPF #414] fixes issue description diff

- fixed journals_controller#diff
- adapt redmine diff helper for new diff markup
specs

- new specs for journals_controller#diff
- ported journal_formatter specs from old test repo
don't render absolute attachment links, it's not necessary and breaks on tests
fixin diff_spec and attachment_spec:

* using correct translations
* fake journaled classes translation
Merge branch 'feature/rails3_fix_issue_description_diff' into feature/rails3

Conflicts:
	spec/lib/journal_formatter/attachment_spec.rb
	spec/lib/journal_formatter/diff_spec.rb