Improve Consistency of Transform Primitives

[WillKoehrsen]

Due to the use of a frozenset which is an unordered Python object, the order of commutative transform primitives that used multiple columns, such as AND, could change when running Deep Feature Synthesis in different Python sessions. This behavior did not affect the feature values because the primitives are commutative. It did change the feature definitions which made comparing different sets of feature definitions a challenge.

The behavior is addressed by sorting the features used in commutative transform primitives alphabetically by name. For example, if the transform primitive AND is used with the features (columns) FLAG_A and FLAG_B the resulting feature will be AND(FLAG_A, FLAG_B).

[codecov-io]

Codecov Report

Merging #236 into master will increase coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #236      +/-   ##
==========================================
+ Coverage   93.63%   93.65%   +0.01%     
==========================================
  Files          71       71              
  Lines        7671     7690      +19     
==========================================
+ Hits         7183     7202      +19     
  Misses        488      488

Impacted Files	Coverage Δ
featuretools/synthesis/deep_feature_synthesis.py	93.22% <100%> (+0.03%)	⬆️
...ols/tests/dfs_tests/test_deep_feature_synthesis.py	98.45% <100%> (+0.08%)	⬆️

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[kmax12]

Looks good. Merging