[IMP] account: d'ont create journal items for invoice lines with quantity 0 (not amount because of tax)
[IMP] crm: usability kanban view and schedule an activity
[FIX] crm: schedule an activity bug when no activity yet
[IMP] website: app for website (not a menu in website admin)
Activities in opportunities are now handled through a wizard and not through
the form view anymore. The wizard is called via a Log an activity button. The
wizard allows to log an activity and to schedule the next activity. It
replaces the various <next activities> / Done / Cancel link buttons on the
form view that nobody seemed to inderstand.