Store FreeBusySimple and FreeBusyDetailed rights as roles

Map:
   * FreeBusySimple -> PublicDAndTViewer
   * FreeBusyDetailed -> ConfidentialDAndTViewer

Although SOGo is not really used AFAIK, we can now keep it and keep Calendar permission issues consistent.

It requires https://github.com/openchange/openchange/pull/98 to work.