Add TentativeAccept, TentativeReject, Flag to the specification?

[phochste]

To be in line with COAR notify spefication?

The activity types make also more sense than some core AS2 types that are more for social networking activities related to persons (not artifacts): Arrive, Block, Invite, Join, Leave, Listen, Travel.

Some activities maybe could be done by an actor on an artifact but have not really our focus in any of the use-cases: Dislike, Like, Move, View.