Set a constraint on the number of vehicle

[alegaballo]

Is there a way to fix the number of vehicle to use? I think it could be useful to have the possibility to use this constraint.

[oblonski]

related to #239

[braktar]

A constraint on the number of vehicle could be useful in two cases.

• The infinite fleet mechanism, with some vehicles prototypes, the idea is to limit their number but generate the most fitted fleet.
• All the vehicles are defined, but we want a selection of the most fitted ones. This case could be include in the first one if we could limit the number of each prototype

[Levi-Gong]

• prototypes

do you have any example about case one?