Simplify the management of the duration of a meeting

Today, for a meeting there are 6 properties in the MeetingClass that are handling, one way or another, the duration of a meeting:

• duration (type Static List)
• durationHour (type Static List)
• durationMinutes (type Static List)
• durationString (type Textarea)
• calc (type computed field)
• hasBeenEdited (type boolean)

I'm not sure how all these properties are used, but I am positive that we can do simpler.

Also, there is some update of some of these fields, computed from the other fields, upon visualisation of the meeting document (this is what hasBeenEdited is good for), which created issues in the past (see XAMEETINGS-100 ), which I doubt is necessary.

We need to simplify this, I really don't see why an approach with only a start date and and end date would not work, with a computed duration.

Please don't forget about migration of existing meetings to the new format.