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.
Merge pull request #48 from Zentyal/ejhernandez/fix-calendar-perm

Store FreeBusySimple and FreeBusyDetailed rights as roles