These need to be re-done in a way that is more
tolerant of the inherent instability/noise in
the simulated circuits (or more ideally, changed
to test a particular thing that can be more
well-defined rather than just simulating a circuit
and seeing if the numbers come out a certain way)
CHANGED abandon the unpredictable behaviour of the Simulation Command
dialog. You now separately add simulation tabs (which have invariant
command types once created), and the dialog edits the current tab.
Also a bunch of bug fixes to make multiple simulation plots actually
work.