PPMR_plot function has larvaceans and salps hardwired #44
Description
This is causing issues for students in MATH3070*. The PPMR_plot function in fZooMSS_Xtras.R specifies the betas for "Larvaceans" and "Salps" explicitly, which may cause issues if we were to introduce/use different filter feeder groups, and throws an error when they do their sensitivity analysis (specifically, when they set these groups to have a beta instead of PPMRscale).
Suggest to have this look up which groups are listed as FeedType == "FilterFeeder" instead and find the relevant weight classes dynamically.
*I've told them to ignore it and not make this plot in that case. Raising the issue here, since the public repo still has larvacean and salp feeding kernels set by hand.