Length of the long simulation

[cecilehannay]

I believe that we don't need a 4 year simulation for the longer simulation in the basics. One year might be enough and maybe even shorter. We should coordinate with the diagnostics chapter.

[nusbaume]

Just an FYI that I have modified the diagnostics chapter to all use an already-run four year long simulation for all of the diagnostics, instead of depending on the participants' simulation. This way we can shorten the "longer" simulation to whatever we would like without impacting the diagnostics exercises.