because the name "currentTime()" can be mistaken for the point in
real-life time at which the simulation is run (e.g. March 11, 2014,
15:07:45.123), the _point_ in time which the simulator timer currently
represents (e.g. Jun 5, 1985, 02:33:12.345) instead of the simulator
time in seconds which elapsed since the START date
(e.g. 52633.345 s).
this rename may lead to some fallout in other modules. I'll
fix them after this PR has been merged...
Since SimulatorTimer is a fairly shallow shim if using the TimeMap, it
can also be removed relatively easily. Having said this, that would
trigger _many_ changes in _a lot_ of places and I'm not motivated at
all to fight that battle as long as the old parser needs to be
supported. I thus decided that the best way is to add a "wrapper mode"
to SimulationTimer...
The step number is zero before the first timestep has been taken, and
one after. The step number is one before the second timestep has been
taken, and two after. This was not clear from the text.
