Merge pull request #200 in ZP/z-push from bugfix/ZP-779-message-is-suddenly-unread-after-moving to develop

* commit '60b8fbe5':
  ZP-779 Remove unnecessary code.
  ZP-779 Only use folderid prefix in importer if it is the new int one. Fix Fetch() in Zarafa backend to work with new longids.
  ZP-779 Use folderid (if available) in serverentryid to identify message.
  ZP-779 Quick & dirty fix, by prepending the folder sourcekey to each message id. "Fixes" the issue, but is ugly.