Hub events: Calculation of expected handling time?

[kt86]

There are in theory different approaches to calculate the expected handling time (and also the logic, when everything is handled and can continue with the next carrier):

After a vehicle arrives at the hub (and unloads its goods) one could assume, that

1. all goods are handled in parallel, so for each shipment we have that handling time as t_fix + t_var_shipment
2. all goods can only be handled one by one. Since we do not know in which sequence they are handled, we had to sum up the times: but do we need to have i) the fix_time per shipment, and thus sum them also hub: -> n*t_fix + sum(t_var), or is it ii) a fix time per delivery -> t_fix * sum(t_var).

in case of 2: What do we write into the event: The same exp. handling duration for all shipments or the individual one (which is easier for i) instead for ii).

t_fix: fix time needed per handling at hub
t_var: a variable time, depending on the size of the shipment.

One additional remark: It is important, that the handling starts event is thrown at the same time step as its triggering event. Currently, it is triggered by a CarrierTourEndEvent... it may change, once we have CarrierShipments and can use CarrierShipmentDeliveryEndEvent as a trigger. -> see e.g. #44 or #174.