Make LALInferenceReadData to save to file the PSD used for the run

Squashed commit of the following:

commit 1a96f84a97b54d16380248c2075e22a6b6e4957a
Author: Salvatore Vitale <salvatore.vitale@ligo.org>
Date:   Sat Oct 4 23:44:37 2014 -0400

    New version with FFT of TD WF
Redesigned lalinference postprocessing page. Redmine 954