Evaluators check for empty data

[tovbinm]

Related issues
Most of our evaluators never check for empty during evaluate call and fail miserably.

Describe the proposed solution

• Added checks for empty data in Evaluators factory, which return defaults in case of no data was provided
• DRY out Evaluators factory
• Update EvaluatorsTest to use property based testing with Tables. Each evaluators is now being evaluated against non empty and an empty dataset.
• Fix evaluation metrics order in ModelInsights pretty print
• Camel case Brier Score from brierScore -> BrierScore

Describe alternatives you've considered
NA

Additional context
Follows up on PR #176

[codecov]

Codecov Report

Merging #178 into master will decrease coverage by <.01%.
The diff coverage is 87.17%.

@@            Coverage Diff             @@
##           master     #178      +/-   ##
==========================================
- Coverage   86.33%   86.33%   -0.01%     
==========================================
  Files         305      307       +2     
  Lines        9976     9971       -5     
  Branches      343      542     +199     
==========================================
- Hits         8613     8608       -5     
  Misses       1363     1363

Impacted Files	Coverage Δ
...orce/op/stages/impl/tuning/OpCrossValidation.scala	97.67% <ø> (ø)	⬆️
...com/salesforce/op/evaluators/OpEvaluatorBase.scala	92.59% <ø> (+2.11%)	⬆️
...alesforce/op/stages/impl/evaluator/OPLogLoss.scala	69.23% <100%> (ø)	⬆️
...cala/com/salesforce/op/evaluators/Evaluators.scala	100% <100%> (+2.89%)	⬆️
...salesforce/op/evaluators/OpBinScoreEvaluator.scala	96.29% <100%> (-0.14%)	⬇️
...lesforce/op/evaluators/OpRegressionEvaluator.scala	91.66% <100%> (ø)	⬆️
.../com/salesforce/op/utils/spark/RichEvaluator.scala	100% <100%> (ø)
...op/evaluators/OpMultiClassificationEvaluator.scala	94.73% <33.33%> (ø)	⬆️
...p/evaluators/OpBinaryClassificationEvaluator.scala	82.5% <66.66%> (+0.92%)	⬆️
...c/main/scala/com/salesforce/op/ModelInsights.scala	92.62% <72.72%> (+0.37%)	⬆️
... and 5 more

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