Aggregate timeline measures and keep their time positions

[ambroisemaupate]

I follow up #287 pull-request about aggregate timeline. This is an awesome enhancement, but I think we could go further.

Why not merging this two Timeline systems in one.

• First timeline do not aggregate same event measures but give them a position in the timeline.
• Second timeline system aggregates same event measures, but we lose time position information

Here is a possible implementation on Roadiz CMS:

I do not stack measures to keep timing location and ease up debugging when you need to know when a event repeats itself.