Report information on simulation termination

[afmagee42]

Some summaries cannot naively be computed without knowing a bit more about how the simulation terminated.

For example, the cumulative extinction probability Pr(extinct by generation g) isn't valid for the 4th generation of a simulation that hit a maximum number of infecteds wall in the second.

[afmagee42]

I think the sufficient piece of information is the last generation which was allowed to draw infection times for all individuals. This is the last completely-simulated generation, everyone in it had a chance to be detected and to infect others, so this should be enough for most summaries I can imagine.