Do nothing special for OSX addressbooks regarding broken directory and multiple contact folder support.
Just don't use directory and use multiple folders, so it works it least in iOS like it does on "other" clients.
Produce a ctag for "directories" (only tested on iOS 7)
so the client does not become stuck in an endless loop...
Add count to force new value after deleting (when not keeping the deleted items)
After change of event: also show changes to comment
Show everything in html mail in html without escaping
Merge branch 'comment_in_diff_and_html_mail'