Improved format string for reaction datae output times.

The previous code attempted to perform smart formatting
of reaction data output times but was partially incorrect.
This was replaced by a simple formatting statement which
can handle 15 significant digits.
Allow interation numbers up to long long.

While internally iteration numbers where treated as long long,
the parser actually was only able to read iteration numbers
that fit into an int. I changed the parser so it can handle
interation counts of long long.