print version of populationsim during run to help diagnose version issues

[bstabler]

also maybe plot the variance around the mean instead of around the zero axis since it can be confusing when the mean appears beyond the variance range.

[bettinardi]

Two separate issues here. I think a phase 9 issue should be to print the version of PopSim to the screen (if I understand the title right). Ben's also around improving the validation reporting - I would ignore that in this issue. I can be opened in a separate issue if partners want to support the idea.