Split the "agenda publcation" into "temporary" and "definitive" agenda publication

[gdelannay]

EGW users needs to have two stages in the publication of a meeting agenda: a temporary publication (after this, groups may still add late items and annexes to existing items) and a definitive publication (after this, only MeetingManagers? may still add late items and add annexes to any item).

So it has been decided to include this into PloneMeeting? directly. In subproducts that do not need those two publication stages, they will still be able to use the standard PloneMeeting? workflows if they redefine some workflow actions for triggering automatically some transitions.

We will need to add a state in the meetingitem_workflow and a state in the meeting_workflow.