Update sampler plotting method

[Chris-Pedersen]

Now that chainconsumer can overplot priors, I will rewrite the sampler plotting script to use that rather than the corner package. Will also add some methods that will make it easier to plot joint chains, as I reuse the same syntax a lot in the current notebooks

[Chris-Pedersen]

The majority of this is done in #81 , but at some point I will also add the option to overplot priors