Add log error metrics

[chris-mcdo]

Issue #, if available: #2621

Description of changes: add log error metrics (MALE, MSLE, EMALE, ERMSLE) to the evaluation and ev packages. Resolves #2621.

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[jaheba]

Thanks!

Let's add the geometric mean: #2640

[lostella]

I think what's needed is the geometric mean of the predicted distribution

[chris-mcdo]

I think both would be useful (geometric mean of the predicted distribution, and geometric mean as an error aggregator)?

E.g. if aggregating the EMALE (= exp(MALE)), you would want to use the geometric mean, since it's a ratio / multiplicative factor