Photosynthesis: Added plot.photo to make response curve plots with CI an...

...d PI. Reorganized the output from fitA to split MCMC into params and predict components for the parameters and states respectively. This makes it easier to do diagnostics & plot on the parameters. Changed variable names for the betas to include the covariate column name (instead of just sequential numbering) and made the output variable list adapt to what variables were defined in the model.