Inconsistent use of `priors` and `prior`

In run_sampler, the argument to give the prior is priors=, while in bilby.gw.likelihood.GravitationalWaveTransient it is prior. To be consistent across the project we should pick one or the other

It is an easy change, but I'm opening an issue to allow people to voice an opinion on whether it should be prior or priors. My vote is priors.

FWIW I prefer priors. One seldom only defines one...

My argument would be that there is only one prior distribution which depends on all of the parameters.

Although given the specific implementation, I won't complain too loudly.

added Refactoring label

mentioned in commit 385587ee

mentioned in merge request !274 (merged)

mentioned in commit 704e7c40

mentioned in commit 791681c4

closed via commit 704e7c40

closed via merge request !274 (merged)