Rv grid shift

[karllark]

Should shift grid to have a point at Rv=2.74 so that f_A = 0 is an allowed grid point. This Rv is the Rv for the SMCBar. This shift needed due to the "triangular" prior on Rv_A and f_A.

rvs = [1.74, 6.24, 0.5]
rv_prior_model = {‘name’: ‘flat’}