License branch

This is a big pile of changes to get rid of Numerical Recipes subroutines thus making the code GPL-able. In the process a few other oddities/bugs/vestigial subroutines were cleaned up. There should be no changes to the output visible to the casual user.

That being said, the biggest change was swapping out the FFT routines from NumRec to FFTW.
These have different conventions, so anyone who cares about the units on the amplitude of whitened waveforms (for PE and waveform reconstructions) might want to look with a critical eye.

I think that the current code is more intuitive w/ it's normalizations of FFTs, and maybe even cleans up some downstream hackery, but please be on the lookout.

I tested on GW150914 using 4- and 8-second segments from BW through megaplot and the output looks good.

Addendum: @sudarshan-ghonge I'm going to go ahead and merge this. Could you please update your copy of master and run one or two of the waveform comparisons as a sanity check on units.