Improved comment management

There’s a change in how users can manage task comments. Ever since TaskBeat has been released to public there’s a role based security model in place. Users sharing the same role are allowed to makde free changes which promotes open communication and trust within workgroups. Today we’ve made a small change to this model. From now on users are allowed to delete only last comment in task conversations, so that users can never accidentaly corrupt the conversation thread.