Resolve #430 (Add normalisation flag to constrained prior)

This MR resolves issue #430 (closed) to properly normalize ConstrainedPriorDict.prob() when sampling the prior. This MR allows for users to input a normalisation flag when creating an instance of a Constraint prior and when calling ConstrainedPriorDict.prob() if there are normalisation constants given will return the normalisation*prob and otherwise use the ratio of total samples to kept samples as this normalisation constant. Pass normalisation=1 when creating a Constraint Prior for behaviour before this MR.

bilby/core/prior/dict.py

@@ -416,7 +416,6 @@ class PriorDict(dict):
                            for key in sample], **kwargs)
 
         ratio = self.normalize_constraint_factor(tuple(sample.keys()))
-        #print("ratio = {}".format(ratio))
         if np.all(prob == 0.):
             return prob
         else: