Minor fixes/ improvements to evaluators

[eacharles]

1. DistToPointEvaluator should be protected against hdf5_groupname being none
2. Evaluator base class should search cached data for keys that include the estimator name, but not require exact matches, this is because we can cache data, e.g., from multiple point estimates
3. Evaluator base class should implement actually using self.config.exclude_metrics if 'all' is in the set of metrics to use
4. Base class parameter limits should be passed to various metrics c'tors

[eacharles]

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