Custom primitive kwarg fix

[rwedge]

Setting custom primitive function inputs via keyword arguments no longer changes keyword arguments for all instances of that custom primitive. Also renamed PrimitiveBase._get_name to PrimitiveBase.generate_name to avoid confusiong with PrimitiveBase.get_name

[codecov-io]

Codecov Report

Merging #38 into master will increase coverage by 0.01%.
The diff coverage is 93.33%.

@@            Coverage Diff             @@
##           master      #38      +/-   ##
==========================================
+ Coverage    88.1%   88.12%   +0.01%     
==========================================
  Files          71       71              
  Lines        6792     6828      +36     
==========================================
+ Hits         5984     6017      +33     
- Misses        808      811       +3

Impacted Files	Coverage Δ
featuretools/entityset/entity.py	76.47% <ø> (ø)	⬆️
...sts/feature_function_tests/test_direct_features.py	100% <100%> (ø)	⬆️
...turetools/primitives/aggregation_primitive_base.py	95.55% <100%> (+0.1%)	⬆️
featuretools/primitives/primitive_base.py	76.94% <100%> (ø)	⬆️
featuretools/primitives/cum_transform_feature.py	97.59% <100%> (ø)	⬆️
...ols/tests/feature_function_tests/test_agg_feats.py	98.47% <100%> (+0.12%)	⬆️
featuretools/primitives/binary_transform.py	83.83% <100%> (ø)	⬆️
featuretools/primitives/transform_primitive.py	97.3% <100%> (+0.47%)	⬆️
featuretools/primitives/aggregation_primitives.py	92.1% <100%> (ø)	⬆️
featuretools/primitives/direct_feature.py	95.45% <100%> (ø)	⬆️
... and 3 more

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[kmax12]

Good change. Looks good to merge