repopulated notebook directory
added opo pure python files
added numerical calculation of drag based on gradient method and optimized version of linear response
now plotting slices though lin resp in mom and real space
setting signal and idler to 0 should reproduce pump-only results
setting signal and idler to zero manually seems to work
created python file for implementing analytical pump-only formula
added python source for the runge-kutta GPE solution
added input file for RK GPE solver
completed replacing single-call fortran routines before integration
nicer error msg for lacking input
fixed pdb size bug
checking pump and kinetic energy against fortran results