Randomised -> non-randomised PIT for count values

[sbfnk]

We're currently using the randomised version of PIT for count values - however Czado et al. (2009) recommend a non-randomised version, plotting

I can't see a reason why we wouldn't use that version instead.

This could be addressed when addressing #359

[nikosbosse]

Love it!

[nikosbosse]

Adding the following comments from @sbfnk from #916:

There were two broader questions raised by this work:

• the way get_pit and plot_pit interact makes addressing Randomised -> non-randomised PIT for count values #913 impossible - the nonrandomised method requires the bins to be known at the time the PIT is calculated
• the way quantiles are plotted when the breaks don't coincide with the quantiles levels in the data doesn't really makes sense (only the ones that coincide are plotted). It might be nice here to make a (e.g. linear, optional) interpolation of the CDF, in which case we could plot a PIT with arbitrary breaks

Both of these cases could be solved if the get_pit() method is changed to take the bins/breaks as an argument, all calculations/approximations are moved there, and plot_pit just plots the resulting geom_col (which may or may not even be needed as a separate function - e.g. get_pit could have a plot argument or else it could just be left to the user). I would suggest to make this change (in a separate issue/PR combo).

[nikosbosse]

I really like these suggestions and think ideally we should address them before the next CRAN release