Fix metric evaluation without inverted target transforms bug

[HunterMcGushion]

• The problem was that metrics were evaluated using the transformed targets/predictions after performing target transformation (QuantileTransformer) via EngineerStep
  • This resulted in metrics that were way too impressive compared to Experiments without target transformations because they were being calculated in the transformed target space, rather than the original/inverted space
• To address this, Environment.__init__ has a new save_transformed_metrics kwarg--moved from settings.G
• Default for save_transformed_metrics is chosen based on the dtype of train_dataset's target data
• SparkNotes version of documentation:
  • If all targets are numeric, save_transformed_metric=False
  • Else, save_transformed_metric=True

[codecov[bot]]

Codecov Report

Merging #169 into master will increase coverage by 0.18%. The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #169      +/-   ##
==========================================
+ Coverage   93.88%   94.07%   +0.18%     
==========================================
  Files          46       46              
  Lines        4939     4958      +19     
==========================================
+ Hits         4637     4664      +27     
+ Misses        302      294       -8

Impacted Files	Coverage Δ
hyperparameter_hunter/settings.py	93.54% <ø> (-0.21%)	:arrow_down:
hyperparameter_hunter/utils/learning_utils.py	100% <100%> (ø)	:arrow_up:
hyperparameter_hunter/environment.py	98.79% <100%> (+0.06%)	:arrow_up:
hyperparameter_hunter/callbacks/evaluators.py	100% <100%> (+16.66%)	:arrow_up:
hyperparameter_hunter/experiments.py	92.05% <100%> (ø)	:arrow_up:

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[coveralls]

Pull Request Test Coverage Report for Build 751

• 35 of 35 (100.0%) changed or added relevant lines in 4 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.2%) to 94.07%

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Totals
Change from base Build 747:	0.2%
Covered Lines:	4664
Relevant Lines:	4958

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💛 - Coveralls