Made the plotting function uniform into accepting both CPMG and R1rho data.
Also made a function to return data, depending if it is data, back calculated, interpolated or residual.
sr #3124(https://gna.org/support/?3124): Grace graphs production for R1rho analysis with R2_eff as function of Omega_eff.
sr #3138(https://gna.org/support/?3138): Interpolating theta through spin-lock offset [Omega], rather than spin-lock field strength [w1].
