hyper-parameter estimation likelihood

Several people (@colm.talbot, @gregory.ashton, @grant.meadors) have urgent need to do hyper-parameter estimation with tupak. There are multiple applications, but we should create a single function that can be adapted to all of these applications.

I recommend that we create a python function to do this. The inputs should include

• The number of events.

• Lists of posterior samples.

• List of parameters described by hyper-parameters.

• List of hyper-parameters.

• The prior that was used to generate the posterior samples.

• The conditional prior.

• Create general tupak.hyper-pe function.

@sylvia.biscoveanu