suzerain: #3052 add functionality to read from and write to file the amplitude growth rate parameters

git-svn-id: https://svn.ices.utexas.edu/repos/pecos/suzerain/trunk@44052 0bd85f0b-c151-43b9-a1e9-27231104551f
suzerain: reduce to single blank line

I'd had "foo\n\n\nbar" instead of "foo\n\nbar".  Gnuplot dislikes
the former which messes up automated #2399-related postprocessing
while working on #2979.

git-svn-id: https://svn.ices.utexas.edu/repos/pecos/suzerain/trunk@44053 0bd85f0b-c151-43b9-a1e9-27231104551f