FR: handle running events in event-list module more flexible

[asaage]

There are different opinions on how to deal with running events as they are not "upcomming" and not "past".
i suggest to add a checkbox as described here

[leofeyer]

As discussed in Mumble on October 6th, there should be a setting "show running events as upcoming" in the event settings, which is then considered in the CalendarEventsModel::findCurrentByPid() method.

[asaage]

kind of tricky...
in case this will be realised with an event-attribute
i'd appreciate an aditional eventlist-format "running events" besides all, upcomming and past
to be able to have closed events that already started not to show up as upcomming in one list but in a separate one as currently running.

[leofeyer]

See #8497.