System.cpp: Pretty math expression total force.
dataReader.py: Took R0, fixed axes skipped meta.

Since datafile now includes meta-section at top, skip this when finding
positions.

Reader now also finds R0.

When animating the axes is set to range from -2*R0 to 2*R0 in order to
better illustrate size of cluster.
TODO: Problem with scaling is found. Need to adjust units, both time and
grav constant. Motion does not seem plausible.
main.cpp: Esthetics.
System.cpp: System now writes a header section to file.