Disable prior samples

In this MR, I've added a flag that can be passed on the command line to disable prior sampling for bilby result files. This speeds up the time it takes to generate the summary page, and circumvents any issues that might arise when trying to sample from user-defined priors, constrained priors, etc. This defaults to true, but it has no effect on LALInference result files or existing PESummary metafiles. I've tested it for both the GW (https://ldas-jobs.ligo.caltech.edu/~sylvia.biscoveanu/tupak/psd_sampling/150914/home.html) and core (https://ldas-jobs.ligo.caltech.edu/~sylvia.biscoveanu/tupak/sgrb/pesummary/html/hyper_100_power_law_cpnest_hyper_100_power_law_cpnest.html) modules, and it ran successfully. I'm happy to run any other suggested checks!