Updating `ModelProbabilityEstimator` class.

Updating to estimate the prior probability of all possible values of the
number of divergence event (rather than just one particular value).
Adding `ModelProbabilityEstimatorTeam` class.

Adding `ModelProbabilityEstimatorTeam` class to the `teams` module.
This class manages parallel processing of `ModelProbabilityEstimator`
instances, and collates and summarizes the resulting prior probabilities
for an arbitrary number of config files.
Updating `dmc_estimate_prior_probs.py` script.

Much of the work that was previously done within this script is now done
by the new `ModelProbabilityEstimatorTeam` class. Updating script
accordingly to simply create and run an instance of this class.