Rework a little the active milestone/all milestone filtering
    
    So we want either only the active milestones, or all of them, so this
    is a simple boolean, if we want only the active milestones then we
    retrieve the list of all the active milestones (ie: having at least one
    ticket open) and consider only this list.
    Otherwise, we get the list of all the milestones and consider this list.